I just installed a new alternator, and whenever i fist stanrt the car, to an idle, the volt gauge only reads 12 volts(just running off the battery i suppose) then when i rev it up a bit, to say about 3-3.5 the volts jump from 12 to about 13.8. and it stays this way when it returns to idle. This never happened with my old alternator, i also just put in a new battery aswell. I have also tried tightening and losening the belt. And clues?

Thanks alot, Matt

 

Hrm... my meter will jump up about the same when I rev the engine, but it usually comes back down, i'm not sure as to why it stays around 14 volts tho

 

Matt, this is normal operation for all good working alternators. There is some good explanation for why this is, I have seen it on the internet, but suffice it to say, this is how all good working alternators operate.

Joe

 

If you are going by the dash gauge, don't, it could be wrong. Use a "real" meter and check at the battery. Check the voltage with the car "off" (to see what the battery has), then start the car and check again (it should be higher if charging). The battery should read about 12.6 volts if fully charged. If it does, then it should read at least 13.2 volts when running, at idle, with no accesories on. If the battery is not fully charged then the "charging voltage" may be less, but it should still increase over the "off" voltage. Without lights or accessories on, it should still be charging at "idle".

 

Mine does the exact same thing. I have a new battery, alternator, upgraded power wires with gold plated terminals, etc. When I first start the car, it sits at about 12.5 volts as long as I dont rev it. As soon as it goes over exactly 2K it goes to 13.8 and stays no matter what I do or have turned on after that. So, youre not the only one. I just live with it, no big deal. One of my other new alternators didnt do it, so I was worried at first, but I dont have any problems with it, so I guess its ok. I have a lifetime warranty too, so if it screws up, Ill just get another one .

~T.J.

 

It is because the old altinators on our cars are not governed, at idle they produce less then at higher RPM. A newer altinator has a governing circuit allowing it to produce the same amps and all all thru the RPM range.