We dismantled the alternators, carrying out a visual inspection on all parts and making sure they looked correct.
Rotor winding to ground test
In this test, we had to use our multimeters on 2K. We placed the black test lead on the centre of the rotor shaft and place the red test lead on the slip rings. In theory, there should be no circuit reading between these parts. If it happened that there was a ciruit, the rotor winding has shorted itself to ground and would need to be replaced. Our meter showed infinity (0), which is a pass.
Rotor winding internal resistance test
We had to set the meter to Ohms at 200. We had to test for internal resistance by touching the two leads together, once we have this reading, we must remember that we have to take away the internal resistance of the meter from the actual resistance reading. We placed each end to the slip rings and obtained the reading, which had to be between 2 to 6Ω
Meter reading - 4.0
Less internal meter resistance - 00.2
Actual - 3.98
This reading gave it a pass result.
Testing the stator winding to ground resistance
For this test we had to set our Ohms meter to 200 and test for internal resistance like before. We had to connect the black lead to the common terminal, which is the point with the most wires. We then connect the red lead to each other terminal one after the other and record the resistance, they should all be the same in theory, ranging from 0.00 - .2 Ω
Meter reading - 0.03 Less internal meter resistance - 0.02 Actual - 0.01
Meter reading - 0.03 Less internal meter resistance - 0.02 Actual - 0.01
Meter reading - 0.03 Less internal meter resistance - 0.02 Actual - 0.01
All our results were within specification and that gave that test a pass result for all three.
The next test we did was testing whether there was any circuit between the stator winding and the ground (body of the alternator) to do this, we set our meters to 2K and placed the red lead onto the common terminal and the black lead to the body of the alternator. The specifications for this are infinity, as there should not be any reading, which is the result we had, meaning that our stator had not shorted and would not need replacement.
Testing the rectifier positive diodes
For this test, we had to place our meter onto the diode testing symbol. We placed the black test lead on the B terminal and touched the positive lead on each of the P terminals, in order to obtain our readings. There should be very low resistance in all of them. We then had to place the positive lead onto the B terminal and touch the black lead onto each of the P terminals, the resistance should be quite high.
Results for positive diode testing with black lead on B
Terminal 1 - .603
Terminal 2 - .605
Terminal 3 - .593
Terminal 4 - .600
The specification for the test above was 0.5VD to 0.7VD, meaning that all of our terminals passed.
Results for positive diode testing with positive lead on B
Terminal 1 - 0
Terminal 2 - 0
Terminal 3 - 0
Terminal 4 - 0
The specification for the test above is infinity, or 0. As the results show, all of our terminals passed.
Testing the rectifier negative diodes
Using the same testing mode as before, place the common lead onto the terminal known as 'E', then touch the positive lead onto each of the P terminals. The resistance should be high on each terminal. Then place the positive lead on the 'E' terminal, and the ground lead to each of the other terminals. Resistance should be low.
Results for the negative diode testing with the ground lead on 'E'
Terminal 1 - 0
Terminal 2 - 0
Terminal 3 - 0
Terminal 4 - 0
Specification for the above test was 0, or infinity, meaning that each of the terminals passed.
Results for the negative diode testing with the positive lead on 'E'
Terminal 1 - .582
Terminal 2 - .630
Terminal 3 - .588
Terminal 4 - .592
The specification for that test was 0.5VD to 0.7VD, meaning that each terminal passed this test as well.
Testing the voltage regulator
To test the voltage regulator in the alternator we use a Transpo voltage regulator tester. To use the tester, we set the voltage controls to 12v and set the current field switch to 0.5amps. Before we can continue though we must find the appropriate information on the voltage regulator in our workbooks, this included wiring diagrams and information charts on each of the different types of regulators.
Wiring diagram for the voltage regulator being tested
Next, after reading the given information on the voltage regulator tester, we must set the 'Field' switch to either 'A' or 'B', which ever the data says for that particular regulator. Then we connect the test leads according to our wiring diagrams. Once this is complete, we can turn on the unit. If the short circuit lamp turns itself on, that means that there is a short circuit happening, in the event of this you must turn off the unit immediately. The field circuit lamp indicates regulator switching frequency, this LED should flash rapidly. The warning light circuit simulator should come on and stay on. The voltmeter should indicate the set voltage according to the information chart for the regulator + or - 1 volt.
Regulator specifications
Part number : IN224
Field setting : A
Voltage: 12v
Set point spec : 14.6
Regulator results
Short circuit light off? Yes PASS
Warning light on? Yes PASS
Field light flashing continiously? Yes FAIL
Set point vantage reading: 12.1 FAIL
The data gathered shows that the voltage regulator is not regulating the voltage properly through the alternator, shown by the field light not flashing continiously as it should. This conclusion is also backed up by the set point vantage reading only being 12.1v instead of the specification of 14.6v.
Checking the brush protrusion length
To check the brushes of the alternator, we use a vernier calliper to measure the brushes, making sure there is enough length. The brushes are important because they supply electricity to the slip rings and if they are too short the brush springs cant apply enough pressure to maintain the constant contact that is needed, causing excess sparking that damages the slip rings and reduces the output of the alternator. We measured the brushes between the slip ring contact face and the face of the brush holder.
Brush 1 - 15mm PASS
Brush 2 - 15mm PASS
The specification for the brush length was 4.0mm minimum, meaning that they passed.
Overall Alternator Report
The rotor winding to ground test came back as a pass, meaning that there was no ciruit and it had not been shorted. The internal resistance test came back within specifications. The stator winding resistance test came back within specification, with the overall resistance of 0.01Ω. The stator to ground test showed a pass result, meaning that the stator was in perfect working order. The rectifier positive diode tests were a pass as well as the negative diode tests, meaning that no furthur action needs to be taken in regards to them. The voltage regulator test was not as successful, as the field light for the tester which indicates regulator switching frequency, was not flashing indicating that the alternator is not regulating the voltage, meaning that the set point voltage is 12.1v instead of 14.6v. The brushes are in good condition and require no attention. The bearings, although not tested, should be replaced as a precaution. If this were on a customer vehicle I would repair/replace to voltage regulator or quite possibly the whole unit depending on any further tests that could be undertaken.
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