Alternator Off Car Testing

Alternator is a device which converts ac to dc cause it is of no use directly for the battery.  In alternator off car test we took the alternator and DISMANTLED it in the following way

• Removed the nut on Terminal and insulator
• Removed the 3 nuts that hold the rear cover, remove the rear cover
• Removed the brush holder and voltage regulator
• Removed the 4 screws that hold the rectifier, remove the rectifier

we then did the Rotor Winding to Ground Test in this we set the multimeter on 2K then placed the black lead on the centre of the rotor shaft. Placed the red lead on slip ring. There should be no circuit in between these points so the spec was infinty and it was found to be infinity so it was alright.
Then we did the rotor winding internal resistance. We set the meter on 200 ohms, tested the internal meter resistance by touching the 2 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 is 2ohm to 6 ohm. The readings came out to be 2.9 ohms so it fall between the spec so it passed the test.
Then we did tested the stator winding  resistance. We set the meter at 200 ohms  and then testwed the internal resisitance of the meter.Then we selected tbhe common terminal of the stator winding terminals A to D. Connect the black lead to the common point. Connect the red lead to the other terminal one after the another and record their their resistance they should be approximately the same from 0.0 ohm to 0.2 ohm
All the readins were between the spec so it passed. Then we ste the meter at 2k. Placed the red lead of the meter on the common stator winding terminal and the black lead of the meter on the body of  alternator. There should be no circuit between the staotr winding and ground. The meter should read infinity and if there is a circuit then the stator has grounded  and requires replacement
Then we tested the rectifier positive diodes. We set the meter on diode test mode. Put the common lead onB 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.
Then we did the Rectifier Negative Diodes. We set the meter on doide test mode. Put the common lead on E terminal. Then touch the common lead on each of the P terminals and record the readings.
Then we checked the brush protusion length.In this we used a vernier calliper it should have been over 4mm and one was but the other one wasnt.
After all these tests i could say that the alternaotr passed the rotor winding to the ground test. the internal resisitance of the rotor winding was also ok so it passed. The positive diodes of the rectifier had some problem cause they failed the testand while testing the negative it was ok so it passed the test. The voltage regulator was also working alright.When we checked the brush protusion then we found that 1 was alright and the other one was bit short and needed replacement