Alternators

Alternators are what powers the cars eletronics and charges the battery when the car is running. It is run straight from the crankshaft by a belt.

The first test we did was a visual check for any damage on the outer case. Then we removed the rear cover to expose the components. we then removed the brushes, the regulator and the rectifier.

I carried out a test to make sure the rotor shaft and the slip rings have no circuit between them. I placed the multimeter set to Ohms, one lead on the rotor shaft and one lead on the slip rings. The meter should read infinity meaning that there is no circuit between the two. There was no circuit.

Testing the rotor winding internal resistance I touched one lead to one slip ring and the other lead to the other slip ring. The reading should be within 2 and 6 Ohms. I got a reading of 2.8. This was a suitable reading which means it has passed.

Testing the stator winding resistance I connected the black lead to the common point and then touched each of the other terminals one after the other. the readings should be within 0.0 and 0.2 ohms. I got a reading of 0.0 Ohms. Then to test the stator winding to ground I attached the red lead to the common terminal and the black to the body of the altinator. There should be no connection so the reading should be infinite. This is what I got so there is no connection between the stator windings and the altinator body (ground).

Testing the rectifier diodes. Setting the multimeter on diode test mode I placed the common lead on the B terminal and touched the positive lead to each of the P terminals (where the diodes conect to the stator windings). I recorded my readings. The readings were all within the specs of 0.5-0.7 except one. The one that failed I got a reading of infinity, this was because it was the common point and has no connection to the B terminal.

If I put the cables on the opposite terminals I got an infinite reading for all of the diodes. This is beacause diodes only let electricity flow one way in a circuit.

Testing the Negative diodes is almost the same only touching the negative lead to the E terminal (body of the rectifier) and the postive to each of the P terminals. I should have got an infinite reading for each of the diodes which I did. Testing with the leads swapped over, I got readings which were in the specs of 0.5-0.6.

Measuring the brushes they should all be above the minimum length of 4.0mm. My brushes were both at 6.0mm.