Hey guys im having some problems with my 94 3.9 5 speed dakota the amp gauge will drop down to 8 and then the check engine light will come on. I took the alt off and took it up to autozone and tested it and it came back good. If i rev the truck to 4 or 5 grand the gauge will shoot back up to normal. Would this be a voltage regulator problem? If so i know the regulator is built into the ECU so i would have to replace it or is there a way to wire an external regulator to it? Or is there any other components that would cause this? Any and all help is greatly appreciated thanks!

 

The autozone quick test can be inaccurate sometimes, if the alternator is not completely dead. Lets just say it's dying but not completely dead yet.

90% of the time it passes the autoparts stores tests and it still can be bad. I would suggest to buy one and test it out. But first you may want to check your wiring, make sure you have contiuity on all wires and their outputs.