Testing Diodes

Background to, measuring diodes:

Diodes allow electricity or current to flow in one direction, and stop current flow in the other direction. The arrow points in the direction of flow for conventional flow of electricity, from positive to negative.

When a diode is connected to a voltage source so that current flows, it is called "Forward Bias". In this direction, theelectrons and "holes" are pushed into the middle boundary layer so the electrons can flow through the "holes".

Although we often say electricity flows from positive to negative in conventional theory, it is also true that the electrons actually move from negative to positive. This is called electron flow theory. While the positive charge of the missing electrons, or "holes" are pushed from positive to negative, the electrons ars pushed from negative to positive and can conduct through the "holes" that have a missing electron, and so attract an electron.

This enables electricity to flow through a diode when it is forward biased.

When a diode is connected to a voltage source in the other direction current does not flow. This is called "Reverse Bias".

Once  current starts to flow through a diode, there is not much resistance to current flow. There is some voltage drop caused by the electromagnetic push required to get the electrons moving. And there is heat created by the small resistance to current flow. Diodes used in a circuit will usually have a resistor in series to limit current flow.

Measuring Diode Resistance with Ohm (Ω)

To check a diode, some will try to use an ohmmeter to check its resistance. A diode should flow in one direction, and not in the other direction. So maybe you can see this with an ohmmeter? The problem is most digital ohmmeter do not put out enough voltage to reliably get through the boundary layer. In other words, they don't put out enough voltage to "turn on" the diode. Older analogue ohm meters often will put out enough voltage in the ohm tset position to be able to "turn on" the diodes.

With a proper analogue meter in ohm position, the resistance will be low when the meter is flowing in forward bias direction, and the resistance will be very high or infinite in reverse bias direction.

Measuring Diodes with "Diode Test"

The most reliable way to check a diode with a digital meter is with the "diode test" position. In this position a higher voltage is used and the meter shows the voltage drop required to push through the boundary layer.

In the forward bias direction, the meter will read the voltage required to push through the diode and "turn it on". In the reverse bias direction, the meter will read the maximum voltage it can put out since there is no flow. If the diode is broken, creating an open circuit, the voltage rises to the maximum output of the meter in the diode test position.

1.Identify the direction of flow through the diode you are given by drawing a simple picture and the symbol for a diode. Identify the ends as anode and cathode on both the picture and the symbol. Also show the direction of current flow.

2. Measure the Resistance ( Ω) of the diode in both directions using  the 2KΩ position on the meter:
Anode to Cathode: Infinity
Cathode to Anode: Infinity

2.1 Check the voltage supplied at the meter probes in the ohms position? With another meter set om DC volts while the meter is set on 2K ohms position.
Record here: 0.25V

2.2 Is this enough voltage to theoretically push through the bindery layer of the diode and get an accurate reading?     NO

2.3 Did the ohm measurement work? Describe how effective this was in testing the diode in both direction:
No, the ohm measurement didn't work, this was not enough supplied voltage to theoretically push through the bindery layer of the diode and get an accurate reading on the meter.

3.0 Use Diode Test position to measure the diode  in both directions:
Anode to Cathode: 0.642V
Cathode to Anode: Infinity

3.1 Explain what the Diode Test position readings mean when you test the diode in both directions and describe whether the diode was good or bad:
When I did the Diode Test position, Anode to Cathode, the reading on meter was 0.642V and the reading on the meter of Cathode to Anode was infinity, that's means this diode was good.

4.0 Build a circuit with a diode and resistor. Build the circuit below with a 1KΩ (1000) resistor and use a 12 volt supply, unless told otherwise.

4.1 Measure the voltage drop across the resistor (R)          11.27Vd
4.2 Measure the voltage drop across the Diode (D)             0.69Vd
4.3 Measure amp flow through the Diode                              12mA
4.4 Measure the available voltage at Supply (Vs)                11.96V
4.5 Add the voltage drop across R and D. VDr+VDd=        11.96V

5.0 Apply the Rules of Electricity to these readings above and describe how these readings demonstrate the rules of electricity in action:
When I tested the voltage drop across the resistor it was 11.27Vd and the voltage drop across the Diode was 0.69Vd, the available voltage at supply was 11.96V, the total voltage drop across R and D was same as the available voltage. Which means the resistor and the diode share the supply voltage and when the voltage drop value more 0.6V, the diode got some current flow.

6.0 Change the resistance by replacing the resistor with a higher value resistor to the circuit.

6.1 What size resistor did you put in?                    270KΩ

6.2 Measure the voltage drop across R.             11.50Vd

6.3 Measure the voltage drop across D.             0.44Vd

6.4 Measure amp flow through D.                       0.04mA

6.5 Describr how this change of resistance lead to changes in your volts and amp readings. Discuss how this demonstrates how the rules of electricity work.
When I used 270KΩ's resistor the voltage drop across R was from 11.27Vd to 11.50Vd and the voltage drop across D was from 0.69Vd to 0.44Vd and the amp flow through D was 0, which means when I used higher value resistor, the current flow through diode also getting smaller.

7.0 Test an LED (light Emitting Diode) with a meter in the Diode Test position to measure the LED in both direction:
Anode to Cathode: 1.674V
Cathode to Anode: infinity

7.1 Compare the voltage drop of a normal diode and an LED. What does this tell you?
The LED got higher voltage drop than a normal diode, that's means LED require higher resistance than normal diode.

7.2 Build a circuit with an LED in the diode position, as shown below. Use a 1KΩ resistor and a 12 volt supply, unless told otherwise.

7.1 Measure the voltage drop across R. Record here: 9.92Vd

7.2 Measure the voltage drop across D. Record here: 2.03Vd

7.3 Measure amp flow through LED. Record here: 12.0mA

7.4 Measure the available voltage at Vs. Record here: 11.95V

7.5 Add the voltage drop R+D. Vr+Vd= 1.95V

8.0 Apply the Rules of Electricity to these readings and compare how these readings are different than the readings for the diode above. In other words, how does the difference between a diode and an LED result in different readings for each part?
When I builded a circuit with an LED the voltage drop across R was lower than diode above, the voltage drop across D was higher than diode above. The amp flow through LED, available voltage and total voltage drop R+D were same as diode above, that's means LED require higher resistance than diode and the voltage also require higher than normal diode.

Identifying, Testing and Combining Resitors

Colour identification
Resistors can be indentified by a code using the colour and position of the bands.

First two or three bands may be the numbers to write down
Next band is the multiplier ( how many zeros to add to the number)
Gold multiplier makes one decimal place smaller, Silver makes two decimal places smaller
Last band to right may be tolerance values
Notic the examples on the right
Brown, Red, Orange, Gold=1,2,1000,5%=12000Ω 5%, or 12KΩ
Some people use this saying to help them remember the colour:

bad
beer
rots
our
young
guts
but
vodka
does
without

Indentification and combining practice:
1. Obtain 6 resistors of different values. You are then going to determine their value two ways:
Use the colour code to calculate the value of the resistor.
Measure the resistor value with a multimeter.

Record the values in the chart below
Band Colours            Measured Value              Low Tolerance              HigH Tolerance           PASS/FAIL
and calculations         (multi-meter reading)         Value                             Value
y,v,y, g=0.47MΩ5%     0.464MΩ                       0.440MΩ                      0.487MΩ                   PASS
r,r,y,g=0.22MΩ5%       0.215MΩ                       0.204MΩ                      0.226MΩ                   PASS
br,b,y,g=100KΩ5%      99.2KΩ                         94.24KΩ                       104.16KΩ                 PASS
y,v,o,g=47KΩ5%         46.5KΩ                         44.18KΩ                       48.83KΩ                    PASS
r,r,o,g=22KΩ5%          21.8KΩ                         20.71KΩ                       22.89KΩ                    PASS
br,b,o,g=10KΩ5%       9.84KΩ                         9.35KΩ                         10.33KΩ                    PASS

2. Choose two resistors and record their individual ohm resistance value measured with a multi-meter
          Resistor 1     99.3Ω                                     Resistor 2     469Ω

3. Put these two resistor together in series ( end to end, one right after another) and measure their combined value. Record below:
1 and 2 in series:     568Ω

4. Put these two resistors together in parallel ( conect the ends when they are side-by-side). Measure their combined value. Record below:
1 and 2 in parallel:     82Ω

5. What principles of electricity have you demonstrated with this? Explain:
When put two resistors together in series, the combined value should be resistor 1 + resistor 2, and the toal value should be bigger than resistor 1 or resistor 2. When put two resistors together in parallel, the combined value should be 1/Rt=1/R1+1/R2, and the total value in parallel should be lower than resistor 1.

Relays

Relay:
A relay uses a low amperage circuit to switch on a higher amperage circuit. They are very commo on vehicles, and although there are many types, they are very similar in how they work.

The control circuit will have a coil of wire that creates magnetism when the circuit is powered and earthed. The switching circuit will have a set of point contacts that are switched by having the magnetism pull the points over to connect with another set of points. There may or may not be a circuit that is complete when the relay is "off", or un-powered.

The control circuit usually gets power from the battery. And it will have a switching device in it that will turn the circuit on and off. The switch may be in the positive side or the earth side. It may be switched by a switch, a sensor with a switch inside in, or an ECU (electronic control unit) that does the switching based on a logic circuit.

The switching circuit usually also gets power from the battery. Its circuit will contain the device that needs to be turned on or off. And this circuit will usually end in the device being earthed to provide a complete circuit.

The wiring diagram symbol usually looks somthing like this:
Example 1: Battery power will come in on the left, to power both the control coil and switched circuit. Grounding the coil on the bottom would pull the relay switch points closed. Power would go out the right to power whatever had been switched on. This is a normally open switch.

Example 2 shows a transistor to turn on the controlling circuit. And the switched points are "normally open" but will be closed when the relay is turned

Relays will often have a wiring diagram printed on their cover to show how the relay can be used. There may be unmbers on the bottom to show which pins are connected to which terminals.

Protection Diode: Thecontrol circuit may have a diode or resistor in parallel to lower voltage spikes that can hurt electronic control units. Care must be taken to wire up the control circuit so it does not short the diode. The circuit must be set up so the current reaches the diode in the "reverse bias" direction

Pin designations: Bosch style relays use common pin numbers to designate what they are usually connected to.
86 Positive side of control circuit
85 Negative side of control circuit
30 Battery supply for switched circuit
87a Normally closed switch circuit
87 Other switch circuit
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Relay wiring on Electrical Boards: The diagrams and pictures below show which relay pins relate to the different colored terminals on the relays.

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1.0 Measure Resistance (Ω) in the following circuit: ( measure when the relay is off)
86 to 85     67.4Ω
30 to 87a   0Ω
30 to 87     infinity

1.1 Identify Control Circuit and Switching Circuit: Write the terminal numbers for the circuits below:
Control circuit that switches the points     86,85
Switched points that carry the higher amps     30,87,87a

1.2 Calculate amps that would flow in the control circuit 86 to 85, if 12 volts supply was used. Show your calculations:
I=V/R     V=12V;I=67.4A
I=12/67.4=0.18A

1.3 Is there a switching circuit that is Normally Closed when the relay is off?
YES                    Pin number: 30 and 87A

1.4 Is there a switching circuit that is Normally Open when the relay is off?
YES                    Pin number: 30 and 87

2.0 Draw a wiring diagram in the box below showing a relay circuit controlling three light bulbs in parallel. The switching circuit of the relay must turn on all of the light bulbs, and the control circuit of the relay must be negative switched:

2.1 Wire up the Relay on a circuit board so the switching ciecuit of the relay will turn on one of the light bulbs, and the control corcuit of the relay will be controlled by a switch.

2.2 Measure available voltage at the following terminal points when the circuit is off , and then when the circuit is on.
Circuit Off                    Circuit On                    Control circuit
86     11.99V               86     11.94V               current 0.14A
85     11.98V               85     0.02V                 Consumer Circuit
30     11.98V               30     11.93V               current 1.70A
87A  11.98V               87A  0V
87     0V                      87     11.90V

2.3 On which terminals did the voltage change the most? Between the off and on position? Note those that apply
85, 87, 87a

2.4Explain why the voltage change on each terminal of the relay
between the on and off position? Compare and explain:
86. When the switch off, the voltage of terminal 86 was 11.99V, when the switch on, the voltage of terminal 86 was 11.94v,because the load makes the voltage drop 0.05V
85. When the switch off , the voltage of the terminal 85 was 11.98V because that was open circuit, when the switch on the voltage of the terminal 85 was 0.02V, because when the switch on that was close ciecuit, the control circuit gose work and makes the voltage drop to 0.02V.
30. When the switch on, the voltage of terminal 30 droped from 119.98V to 11.93V, becasue the load makes the voltage drop
87A. When the switch off the voltage from positive to terminal 30 and connect to 87A, so the voltage was 11.98V, when the switch on the terminal 87A was not connect to the circuit, the voltage was 0V.
87. When the switch off, the terminal 87 was open circuit. When the switch on, the voltage from positive to terminal 30 and connect to 87, that was close circuit, so the voltage was 11.90V.
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3.0 Draw a wiring diagram in the box below: to wire up a relay to switch between two light, as if you were switching between low beam and two high beam headlamps.

3.1 Wire up a relay with the diagram you drew above to switch between one light bulb and another, as if you were switching between low beams and high beam headlamps.

Alternator off Car Testing

Dismantle:

1. Remove the nut on "B" terminal and insulator.

2. Remove the three nuts that hold the rear cover, remove the rear cover.

3. Remove the brush holder and voltage regulator.

4. Remove the four screws that hold the recifier, remove the rectifier.

5. Remove the four screws that hold the voltage regulator, remove the regulator.

6. Carry out test as scheduled on the following pages.
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Rotor winding to ground test:

Set the meter on 2K. Place the black lead on the centre of the rotor shaft as indicated. Place the red lead on the slip-ring as indicated.

There should be no circuit between the rotor shaft and the slip ring.

The meter should read infinity.

If there is a circuit the rotor winding has shorted to ground and will need to be replaced
Spec     Meter reading     Pass/Fail
Infinity   Infinity                 Pass
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Rotor winding internal resistance test:

Set the Ohms meter on 200Ω, test for internal meter resistance by touching the two leads together. Remember that the internal resistance of the meter must be taken away from the actual reading.

Place one end of each lead on the slip rings as indicated to obtain reading. The reading specification in 2Ω to 6Ω
Spec          Meter reading          Less Internal Meter resistance          Actual          Pass/Fail
2~6Ohms   3.4Ω                       0.5Ω                                               2.9Ω            Pass
Too low that's means winding contact other winding—reduce resistance
Too high that's means insulation dirty not good connection between winding and rotor slip ring.
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Testing Stator Winding resistance:

Set Ohms meter on 200Ω，test for internal meter resistance by touching the two leads together. Remember that the internal resistance of the meter must be taken away from the actual reading. Select the common terminal ( the one with the most wires attached) of the stator winding terminals A to D. Connect the red lead to the other terminal one after the other and record their resistance they should all be approximately the same from 0.0Ω~0.2Ω

Testing stator winding to ground test:
Spec               Meter reading               Less Internal Meter Resistance               Actual               Pass/Fail
0.0~0.2Ω       0.5Ω                             0.4Ω                                                     0.1Ω                 Pass
0.0~0.2Ω       0.5Ω                             0.4Ω                                                     0.1Ω                 Pass
0.0~0.2Ω       0.5Ω                             0.4Ω                                                     0.1Ω                 Pass

Set the meter on 2K. Place the red lead of the meter on the common stator winding terminal (theterminal with most wires connected to it). and the Black lead of the meter on the body of Alternator as indicated by E.

There should be no circuit between the stator winding and ground. The meter should read infinity, if there is a circuit the stator has grounded and requires replacement.
Spec          Actual          Pass/Fail
Infinity        Infinity          Pass
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Testing the rectifier positive diodes:

Set the meter on diode test mode.
Put the common lead on B terminal.
Then touch the positive lead on each of the P terminals and record the reading.

The resistance should be low.

Place the positive lead on B terminal. Then touch the common lead on each of the P terminals and record the readings.

The resistance should be high.

Results for positive diode testing with common lead on B
NO          Spec 0.5VD to 0.7VD          Pass/Fail
1              0.515VD                              PASS
2              0.51VD                                PASS
3              0.51VD                                PASS
4              0.51VD                                PASS

Results for positive diode testing with positive lead on B
NO          Spec Infinity          Pass/Fail
1              Infinity                   PASS
2              Infinity                   PASS
3              Infinity                   PASS
4              Infinity                   PASS
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Testing the rectifier Negative diodes

Set the meter on diode test mode. Put the common lead on E terminal. Then touch the positive lead on each of the P terminals and record the readings.

The resistance should be high

Place the positive lead on E terminal. Then touch the common lead on each of the P terminals and record the readings.

The resistance should be low

Results for negative diode testing with common lead on E
NO          Spec Infinity          Pass/Fail
1              Infinity                   PASS
2              Infinity                   PASS
3              Infinity                   PASS
4              Infinity                   PASS

Results for negative diode testing with positive lead on E
NO          Spec 0.5V to 0.7VD          Pass/Fail
1              0.542VD                           PASS
2              0.542VD                           PASS
3              0.527VD                           PASS
4              0.522VD                           PASS
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Features of the Transpo Voltage Regulator Tester:

1. 12,24 and 32 test voltages at 0.5 and 3 amperes field current.
2. Digital meter with accuracy to within + or -0.1 of a volt.
3. Short circuit lamp if this comes on it indicates a short circuit in wiring system.
4. Field circuit lamp ( small) to indicate regulator switching frequency.
5. Warning light circuit simulator.

Operating Instructions for Transpo regulator tester:

1. Set the voltage control to 12 volts
2. Set the field current switch to 0.5amps
3. Set the "FIELD" switch to "A" or "B" according to the information chart for the regulator
4. Connect the test leads according to the diagram for the regulator
5. Turn the power switch to the on position
6. If the short circuit lamp comes on it indicates a short circuit, quickly turn "OFF" the tester.
7. The field circuit lamp ( small LED) indicates regulator switching frequency, this lamp should flash rapidly
8. The warning light circuit simulator ( the large lamp) should come on and stay on.
9. The volts meter should indicate the set voltage according to the information chart for the regulator + or -1 volt.
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Testing the voltage regulator:

Procedure for testing the voltage regulator, now you have read the extracts from the Transpo regulator test manual on page7.

Locate the wiring diagram for the regulator using the following 3 pages and the numbers on the regulator to identify the correct specifications. If the regulator number dosen't match any specified, use the most common set point voltage for the specification then wire to diagram and test.

Regulator spec's chart

Part Number          M126000-0400  IN220/IN250          Yes/N/A

Field Setting           "A"          Checked                              YES

Voltage                   12          Checked                              YES

Set Point Spec       14.4        Checked                              YES

Now you have checked all the setting, have attained the set point voltage spec and understand how to use the regulator tester, continue to record your finding.

Regulator results  chart

Short Circuit light          MUST BE OFF or turn off tester     OFF          PASS

Warning Light               Should come on and stay on             ON           PASS

Field Lighte                  Should flash continuously                Flashing       PASS

Set Point voltage          Actual reading     14.4                                       PASS

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Checking the brush protrusion length:

It is  important to check length of the brushes as they supply electricity to the slip rings and if they are to short the brush spring can't apply enough pressure to maintain constant contact. This causes excess sparking that damages the slip rings and reduces the output of the alternator. Brushes are measured between (A) the slip ring contact face and (B) the face of the brush holder.

Brush No          Minimum length          Actual length          PASS/FAIL

1                       4.0mm                       5.5mm                   Pass

2                       4.0mm                       4.9mm                   Pass

Instructions for writing your report:

The rotor winding to ground test results was infinity, that's means from rotor shaft to slip ring,  the circuit was open circuit, if i got any reading on the meter that's means it was some problem on rotor winding. The rotor winding internal resistance test: the meter reading was 3.4Ω, the less internal meter resistance was 0.5Ω， theactual reading was 2.9Ω, if i got the result too low that means winding contact other winding, so the resistance was reduce, if I got the results too high that means insulation dirty not good connection between winding and rotor slip ring.

The results about the testing stator winding resistance: The meter reading were 0.5Ω, the less internal meter resistance were 0.4Ω, the actual reading were 0.1Ω. If I got low number which means the stator winding past test, if I got high result which means it not good connection between winding to the terminal, and the testing stator winding to ground test, the results was infinity, which means from stator winding terminal to the body of alternator, this circuit is open circuit.

The result about the rectifier positive diodes were 0.515VD, that means from B terminal to each P terminal were close circuit, when I tested positive diode testing with positive lead on B terminal, the result were infinity, because those were open circuit. When i tested negative diode testing with common lead on E, the result were infinity and the result about negative diode testing with positive lead on E were 0.524VD.

The testing the voltage regulator, my part number is IN220/IN250, I checked the field setting was "A", the voltage was 12V, the set poin Spec was 14.4, when I did the test, the short circuit light was off, warning light was on,field light was falshing and the actual reading was 14.4, so this testing was pass.

When I did the brush protrusion length,the brush 1's length was 5.5mm,so the test was pass,however the brush 2's length just over than 4.0mm, that need replace.

Starter motor on car testing

Make of vehicle     Mazda                    Model     323                    Year of manufacture     1984

Is the vehicle equipped with Automatic transmission?     NO
Is the vehicle equipped with any device that requires a power source for its memory?     NO

If the answer to the above question had been yes: -What would you do before disconnect the battery?
I would insert a 9V battery inside it to retain the memory if the car had cigarette light.

1. Preliminary check before carrying out starter circuit voltage drop tests
a) De-activate the ignition or fuel injection system.     YES
b) Has the battery been checked for serviceability?     YES
c) Have you selected the right range on your meter ( digital)?     YES
d) Is the vehicle's transmission in neutral?     YES

2. Check the OCV of the battery 12.40V Percentage of charge 50%

3. Check the available voltage across the battery terminal while cranking.

Refer to page 80 of Gregory's Electrics and Electronics to obtain the voltage specification while cranking, it is the same as when load testing the battery.
Cranking voltage spec     9.5V
Cranking voltage             11.30V     Pass

If the cranking voltage fails the battery must be retested to determine its condition before continuing with this test.
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Starter Motor Circuit Tesing

Now proceed to check the starter circuit for voltage drop as detailed below.

Refer to the diagram below to obtain the correct position at which to take the following voltage drop reading.

a) Check loss between battery positive post and solenoid starter input stud while cranking.

Spec less than 0.20 volts, Volts drop 0.07 V1     Pass

b)Check loss across solenoid main input and output terminal studs while

Spec less than 0.10 volts, Volts drop 0.04 V2     Pass

c) Check loss between battery negative and starter motor body while cranking.

Spec less than 0.20 volts, Volts drop 0.25 V3     Fail

d) Add all the voltage drop together to find maximum voltage drop

Maximum Allowed 0.50 volts, Total volts drop 0.36 Volts     Pass

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Starter Motor Circuit Testing

3. Checking the starter motor current draw

Refer to fig 7-41 page 101 of Gregory's Electrics and Electronics to obtain current draw specification for your vehicle.

Note:

The chart fig 7-41 is for inertia and Pre-engaged starters only see your lecturer if you have a gear reduction starter.

Starter current draw Spec: 125~150 amps.

To check the current drawn by the starter motor it is necessary to use the inductive ammeter ( Clamp meter) .

a) Set the meter on 400 amps DC and push the Zero Button to zero the meter, if the reading doesn't Zero push the Hold Button and repeat the procedure.

b) Once the meter is Zeroed clamp the pick up around the positive battery lead anywhere between the positive terminal and the "B" terminal of the solenoid.

c) Have someone crank the engine and sa it is cranking push the hold button, this will retain your reading.

Starter current draw 105.8amps          Fail

We had two problenms on this starter motor, one is about the starter circuit for valtage drop between battery negative and starter motor body while cranking, the volts drop result higher than Spec less 0.20 volts, we have to clear the terminal then check it again. Other one is about starter current draw it was lower than starter current draw Spec 125-150amps

Starter circuit test     Fail

Starter motor bench testing and repair

Connecting & what Ground testing a windings tell us:

With the meter set on 2K and one lead connected to any end of the widing and the other to a given earth point as depicted in diagram below

The reading must read infinity this means that there is no circuit between the winding and ground ( earth)

Any other reading means that the winding has shorted to earth.

If it has shorted to earth the winding either needs to be replaced or rewound.
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Connections & result of internal circuit resistance testing windings:

With the meter set on 200Ω connect the 2 probes together and get the internal resistance of the meter and leads for example 0.2Ω. This reading will need to be taken away from the actual reading to give you the true resistance value of the winding.

Connect on probe to one end of the winding and the other to the other end as depicted in the diagram below.

The reading in the diagram above is 3.8Ω but it isn't the true resistance. The internal resistance for example of 0.2Ω must be taken away giving a result of 3.6Ω. This is the true resistance and must be within the manufacturer specification.

There are four possible result that you  can get when doing an internal winding resistance test, they are:

Within specification

Open circuit

Lower resistance than Spec

Higher resistance than Spec

Within specification means that the winding has past this test and can be used again.

An open circuit result means there is break in the winding. This requires that the winding is either replaced or rewound; breaks in winding are very rarely repaired. Refer to the diagram below.

Lowe than specified resistance indicates an internal short result. This means that there is break in the insulation of the winding, it hasn't shorted to ground but has shorted to another part of the winding as illustrated in the diagram below.

This allows the current to take a shorter path through the winding effectively lowering the resistance below Manufacturers specifications

This requires that the winding is either replaced or rewound.

Higher than specified resistance can indicate poor winding connection. This could mean there is dirt or corrosion where the winding ends are connected, thus causes a higher than normal resistance.

Poor connections at the ends of the winding may be able to be repaired by removing them and cleaning up the connection points and re-soldering as necessary

Will be given another starter motor and it should also be tested before dismantling.
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No Load Test:
Mount the starter in a test bench, carry out no load test then enter your meter readings in the chart below.

NO LOAD TEST          MANUFACTURERS SPECIFICATIONS          NO LOAD TEST RESULT
Voltage                          No less than 11volts                                              11.70V
Current                          30 to 50 Amps                                                      37.6A

Label the components:

A. Commutator

B. Roller-type/ overruning clutch

C. Brush spring/ Carbon brush.

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Disassembly:

Disassemble the starter in the correct sequence as demonstrated by your lecturer. Failure to follow the correct sequence and procedures may result in damage to the starter motor.

Sequence:

1. Scribe alignment marks along the two end housings and field housing (main body) of the starter motor, this will help to align the major compinents.

2. Remove M terminal wire from the solenoid ( this wire connects the output from the solenoid to the starter motor)

3. Scribe alignment marks on the solenoid body and mounting then remove solenoid

4. Remove any screws in the commutator end housing ( failure to do this can result in major damage to the brushes or field windings).

5. Remove commutator end housing

6. Remove brushes as necessary to remove brush plate assembly

7. Remove field coil housing ( main body of the starter motor)

8. Remove shift fork from drive end housing ( it is important that you mark the position of the shift fork)

9. Remove the armature assembly

10. Remove the overruning clutch from the shaft ( clean any burrs with emery paper for easy removal of the clutch)

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Testing Armature

Visual Inspection:

Visual Inspection- Check for signs of:

Overheating

Burning

Physical damage of insulation and coil windings

Poling

COMPONENT TEST REPORT

ARMATURE     MANUFACTURER'S SPECIFICATIONS     TEST RESULTS          SERVICEABLE

Overheating        Visual Inspection                                          No signs of overheating     No

Burning               Visual Inspection                                          No signs of burning           No

Physical damage  Visual Inspection                                         The insulation was

                                                                                              damaged onto the poling   Yes

Poling                 Visual Inspection                                          The poling has been

                                                                                              damaged by the insulation Yes

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Ground Circuit Tests:

Use a multi-meter in the ohms range and check for:

Ground Short circuit between each of the commutator segments and the amature core or shaft

ARMATURE GROUND TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULTS          SERVICEABLE

Infinity                                                                    infinity                            Yes

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Continuity Circuit Test

With the ohmmeter in the same range check continuity between one of the commutator segments while moving the second probe around on each of the other commutator segments.

ARMATURE CONTINUITY TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULTS          SERVICEABLE

0-1Ω                                                                     0Ω                                Yes

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Testing Commutator:

Measure the Commutator diameter and check the mica undercut depth as necessary.

COMMUTATOR TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULTS          SERVICEABLE

Minimum diameter 28.8~31mm                              31.5mm                        Yes

Mica Undercut 0.7~1.0mm                                    0.7mm                           Yes

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Check Armature Shaft for run out:

To check for run-out, place the armature between the "v" blocks.

Turn the armature 360° while reading the dial test indicator set up on the armature core as indicated by the arrow

ARMATURE RUNOUT TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULT           SERVICEABLE

0~0.2mm                                                               0.05mm                       Yes

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Alternative Method of Testing Armature

Using 48 volt test Light

Continuity test keep one of the probes on one segment and move the other probe around each of the other segments. ( This test applies greater pressure to the windings and should be used where available) The test light should glow.

Ground test place one probe on any commutator segment and the other on either the armature core or shaft. The test light should not glow.

ARMATURE CONTINUITY AND GROUND TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULT          SERVICEABLE

Continuity Test Light on over each segment            Yes,The light on.          YES

                                                                             The commutater

                                                                             segment are connected

Ground Test Light Off                                            Yes,The light off          YES

                                                                              The commutater

                                                                              segment aren't

                                                                              connceted the armature

                                                                              cove

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Testing for internal short circuit using growler:

1. Place the armature on the "V" of the growler.

2. Turn the switch on to Growler position.

3. Hold a hacksaw blade or metal strip along the armature and rotate the armature.

ARMATURE INTERNAL SHORT TEST

MANUFACTURER'S SPECIFICATIONS          TEST RESULTS          SERVICEABLE

Hacksaw blade will vibrate when placed over         Hacksaw which means          YES

shorted winding indicating a shorted armature         shorted winding indicating

                                                                             a shorted armature 

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Field Coil and Pole Shoes

Visual Inspection- Check for signs of:

Overheating

Burning

Physical damage of insulation and coil windings

Poling

COMPONENT TEST REPORT

FIELD COILS AND             MANUFACTURER'S             TEST RESULTS             SERVICEABLE

POLE SHOES                         SPECIFICATIONS

Overheating                           Visual Inspection                       No signs                          YES

Burning                                  Visual Inspection                       No signs                          YES

Physical damage                    Visual Inspection                       There was a damage         No

                                                                                              for the field coil                      

Poling                                    Visual Inspection                       The field coil has some      YES,can be fixed 

                                                                                              damage                  

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Test the Field coils for Continuity:

Checking for continuity in the field winding place the probes on each end of the field winding

Depending on the design of starter motor circuit, field winding maybe ground or insulated from the field housing.

COMPONENT TEST REPORT

FIELD COILS          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

CONTINUITY         SPECIFICATIONS

If Grounded               TEST N/A                            N/A                              N/A

Not Grounded           0~0.02Ω                              0Ω                                YES

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Test the Field coils for grounding:

Ifthe field winding to ground test can be preformed ( the field winding is not attached to the body of the starter motor). Place the positive probe on the field wire or brush, then the common probe on the body of the starter. The meter should read Infinity.

COMPONENT TEST REPORT

FIELD COILS          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

GROUNDING         SPECIFICATIONS

If Grounded              0~0.02Ω                               N/A                               N/A

Not Grounded          Infinity                                   Infinity                            YES

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Brushes:

Measure the length of the brushes and inspect for cracks and other damage.

Brushes sometimes have a scribed line on one face or refer to specification sheet for allowable length.

Note: When considering the brushes for replacement, remember that the starter may not be removed from a vechicle for over 100,000Km's. If the brushes are close to the minimum you should replace. New brushes are about 14mm long.

COMPONENT TEST REPORT

BRUSHES               MANUFACTURER'S               TEST RESULTS               SERVICEABLE

                                SPECIFICATIONS

MINIMUM             5mm                                          15.9/15.9/15.9/-                 YES

LENGTH

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Brush Holder Assembly

To check for short circuit between insulated brushes and holder set the Ohms meter on the lowest resistance. Place one of the probes on the brush and the other on the metal retaining plate.

COMPONENT TEST REPORT

BRUSH HOLDER          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

ASSEMBLY                  SPECIFICATIONS

Grounded Holder            0~0.02Ω                               0.1Ω                             No

Insulated Holder              Infinity                                   Infinity                           YES

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Solenoid Magnetic Switch:

Identify terminals: "B" Battery Supply, "S" ignition/ starter switch supply and "M" starter motor supply.

Note: M terminal will have a wire going into the solenoid switch

Pull in winding Test:

connect 9V power supply between S and M terminals

Note this test is done with reduced voltage and for a maximum of 5 seconds to prevent heat damage to the winding

COMPONENT TEST REPORT

PULL IN WINDING          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

                                           SPECIFICATIONS

Current Draw                      8~12Amps                            9.1A                              YES

Physical Action                   The Plunger should pull in       The plunger pull in           YES

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Hold in Test

Connect 9V power supply between S and solenoid body

Note this test is done with reduced voltage and a maximum of 5 seconds to prevent heat damage to the winding

Push the plunger in by hand and then release it.

COMPONENT TEST REPORT

HOLD IN WINDING          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

                                            SPECIFICATIONS

Current Draw                       5~8Amps                               10.9A                           No

Physical Action                     The Plunger should                 The plunger was            YES

                                             remain in.                               still inside

                                            When the power is                 When the power is      

                                            disconnected the plunger        disconnected the

                                            should release.                       plunger shoot out

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Pinion gear and Overruning or one way clutch:

Check pinion for gear damage and smooth movement along the armature shaft.

Turn the pinion gear in the direction of motor rotation, the clutch should free wheel and against direct of rotation it should lock.

Brushes:

To check bushes for wear, insert the end of the armature shaft into the appropriate end housing bush to and assess the shaft to bush clearance.

COMPONENT TEST REPORT

DRIVE          MANUFACTURER'S          TEST RESULTS          SERVICEABLE

                     SPECIFICATIONS

Pinion Gear   Visual Inspection                   The pinion gear is good   YES

Bushes          Visual Inspection                   Bushes was damaged      NO

Clutch           Visual Inspection                   Clytch was good             YES

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Assembly:

Re-assemble the Starter Motor:

1. Lubricate the bushes.

2. Assembly in the reverse order of dismantling.

3. Note: Align marks when assembling the shift fork and the two end housings to the field body

4. Hold the brush springs back with a steel wire in the form of book. This will enable brush to be slid on the commutator

5. Do not over tighten any through bolts and screws.

Armature Thrust Clearance:

Check Armature Thrust Clearance. Check the Clearance with seal, spring and lock plate in place.

Pinion to Collar Clearance:

Mount the starter on the  testing machine. Connect power only to S terminal. This will move the pinion out towards the collar without armature turning.

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Final no load test:

Mount the starter in a test bench, carry out no load test then enter your meter readings in the chart below.

NO LOAD TEST          MANUFACTURER'S          NO LOAD TEST RESULTS

                                     SPECIFICATIONS

Voltage                         No less than 11 volts               11.47V

Current                         30~50Amps                            46.7A

Dose the starter motor run within manufacturers specifications YES

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The no load test is good, no any problems. In testing armature, we had some physical problems with the insulation, that was damaged onto the field coil cover. In the ground circuit test, it was gread, no problems and no damages. The alternative method of testing armature also looks good, field coil and pole shoes testing we have same problem as the testing armature, it's about the field coil cover. We broken the brushes when we was doing the brushes test, but we fixed that finaly.