4841 Alternator

An alternator is basically a generator but instead of running on fuel an alternator in a car converts mechanical energy to electrical energy in the form of alternating current (AC).  


On car test 
Voltage (when car is off)=12.6v
Current (No load)=17A
Voltage test (when car is running)=14.6v
Load test (heater on light on)= 45A




Off car test

Rotor winding to ground test
Set the ohmmeter on 2K.  Place the black lead on the centre of the rotor shaft . Place the red lead on the slip-ring.There should be no circuit between the rotor shaft and the slip ring. 
The meter should read infinity O.L

Rotor winding continuity test

Set the Ohmmeter on 200Ω, test for internal meter resistance by touching the two leads together.Place one end of each lead on the slip rings . Result minus  internal meter resistance.The result should be 2-6Ω

Testing stator winding resistance

et Ohmmeter on 200Ω, 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 black lead to the common point.  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 - .2Ω

Testing stator winding earth leakage test
Set the meter on 2K.  Place the common lead on the body of Alternator as indicated.

Place the red lead on the common stator winding terminal (the terminal with more wires connected to it). There should be no circuit between the stator winding and ground.  The meter should read infinity.

Testing 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 readings.The voltage

should be 0.6-0.7 V.

Testing the rectifier negative diodes

Testing voltage regulator

the regulator i tested show a voltage of 12v which is a bad regulator. Good regulator should show 14v

Other ways of testing a alternator

Using a test light tough all the terminals and do ground test. places where should be connected should light places that shouldn't be connected the light shouldn't come on.