I just had my alternator rebuilt. They told me that the stator and diodes were changed. The problem I was having before was that the alternator would start at 14.2 volts and slowly charge up to past 16 volts.

I get the alternator and install it in about an hour.. start the car, 14.4 volts. Leave the engine running for a few minutes, and before you know it, 17.2 volts.

My last battery had died as it only held a charge of 10 volts so I install another battery i had sitting in the garage (charged to 12.6 volts) and it still did this.

Is it possible the battery is causing the alternator to put out such a high voltage? Where is the voltage regulator in the alternator exactly?


Im a little stumped here...

 

sounds like the shop needs to change the voltage regulator in that alternator, as well as the rest of the stuff.
as to where it is inside the alternator, it shows in the service manual, but I don't know personally.

 

thx matt.

i called them and they said they will change that.. but i guess they didnt listen when i told them about it when i dropped it off... oh well

 

If the two batteries are bad, the alternator will put out it's max charge. But 17v sounds really high. Shouldn't go over 15v I believe. I'd have it tested again.

 

Its definitely the voltage regulator. This happened to my last alternator about a month ago. I only had it for a month and the voltage would spike up to 15.5 - 16 volts. I'm sure thats not good for the electronics so i changed it and now it seems to run fine. I also noticed that soon after the voltage spikes, there was a little fluid on my battery. So i'm thinking that the high voltage may have done some harm to the battery.

 

You know what the problem was? The voltmeter I was using(25$) kept telling me that the voltage climbed to 17.
I went back in my car because he wanted to test it while running and the voltage started at 13.8 and went to 14.2 with the throttle open halfway.
Basically my voltmeter is crap and has some sort of capacitance happening and the voltage would keep climbing. Guess I should trust a snap on tester more than a mastercraft voltmeter..

Makes me think twice about the next voltmeter I buy.

 

which voltimeter you have? the cheap radioshack multimeter I have is perfect for what I use it for. never any false readings, I would suggest it. only costs $30.

 

I think its a mastercraft model... ie canadian company.