Last week the alternator went on my car. Had a local shop rebuild it and while I was at it I put a new optima battery in. Got the car all back together and tested the alternator and it was only putting out 11.58v Took the alternator back to the shop and they tested it and it put out 13-14.5v I checked my power wire and all the connections, they all appear to be good. Any suggestions?

 

How did you test it?

 

Engine running one lead on the power wire other lead to ground.

 

its rpm dependant, so you wouldn't be able to test it by yourself.

 

No matter what, if the motor is running, you should be getting atleast 13.5v

 

I would suggest double checking your grounds and then progressing to the voltage regulator circuit, you might have a short somewhere.

 

I double checked the ground and everything seemed ok. I'll have to get to the Voltage regulator circuit.

 

or you could buy an aftermarket alternator, they have come down so far in price, it would probably be the cheapest easiest route at this point. You've already rebuilt yours and that didn't help, which means the regulator is bad, or you have some bad diodes, my money is on an open or shorted diode/diodes, those drop your dc voltage pretty quick. If you have a multimeter, measure your AC ripple current, if you have more than 100mA of AC ripple, toss the alternator in the trash.

 

When the alternator was rebuilt the regulator and diodes were replaced. I basically bought an aftermarket plus a core charge. Buying another isn't an option. It tested good on the bench out of the car but tested bad in the car. There's a bad ground, short, or something in the car.

 

I've been looking and testing. I'm out of ideas. Alternator is good and so is the battery without a doubt. What else can I do?

 

test your connections, make sure your ground cable is good, and also the white cable going from the alternator to the battery is good.