Canada, 85 pickup, diesel. Alternator voltage low(13.4) Found half of diodes bad. Does anyone know if the diodes from gas engine alternator from same year has same internals? I know the cases are different, diesel has vacuum pump built on it. Any ides for souce of parts in can/us for alt would be appreciated. (post for computer/financially challenged friend) Thanks, Mike,Saint John,NB,Canada.(95 3.0 xcab, 245k km,gas pig)

 

Testing rectifier diodes:

1. With rectifier asembly on bench, contact diode plate with one probe and each of the 3 diode leads with other probe. Note ohmeter reading. Reverse probes and repeat test. cCheck all diodes in this manner.

2. All diodes should show a low reading in one direction and NO reading in the opposite direction. If any rectifier diode is defective, replace rectifier assmebly.

Voltage with engine running should between 13.8 - 14.8 volts DC. A pickup with diesel alternator is not the same as a gas pickup.

 

Thanks for the tips, that is what we checked so far. Found one half ie 3 diodes on one side dont pass either direction. Suspect its due to boosting wrong polarity. Has anyone replaced the diodes ine a toy alternator? I figure you buy the plate with 3 diodes bonded to it but have never seen the parts sold. We are trying to get it running today for a quick run to the camp before the ice goes out of the lake. Have access to an 85 gas alt but dont want to tear it apart if it definetly will not work. Thanks again. Mike