just put in a nwe alternator (the other one was shot.) when i run the car in idle the voltage @ the battery was around 17-18 v (i know that's way to high) then when i run @ about 2000 RPM the battery readys about 12 v w/ nothing running... What could it be? Voltage regulator?

 

The reg is in the alternator. Was the battery in low state of charge? ALWAYS charge the battery before making any tests. It is possible for the alt to throttle that high if the battery is low or going bad. Charge the battery or have it tested then retest the charging voltage, if it stays high then exchange the alt. I don't think it's bad though, it is backing down as rpm's increase indicating the overvoltage protect is kicking in. Some units will kick out in excess of 17 volts with a crappy battery or one that needs charging. I have rebuilt Delco alt's for myself and friends for over 30 yrs and I can't tell you how many time a charging problem is overcome by a simple overnight charging of the battery.

 

but, when the car's off and i check the battery it is around like 12.4 volts. does that make a difference?

 

12.4-12.6 is good terminal voltage. If the alt stays that high then I would exchange it for another. 17-18 volts is too high for continous charging. Monitor the voltage at idle after it has been run and check it several times. Average voltage should be about 13.5 14.5 volts.

 

yeah i agree thats why to high, try another one.

 

You might want to make sure that the screw on your battery terminal is tight. I had that problem and it was frying the regulator on the alternator. (mine was stripped). also where did you get the alternator from??

 

i'll check that right away, and i got the alternator from napa.

 

If it is not the screw stipped in the battery than it is the Napa alternator. Their alternators just plain suck. I am on my fourth alternator from them in six months. If it isn't the battery take the alternator back and get your money back. It is not worth the hassle to keep switching out alternators for bad ones. I got so good at changing the alternator that I could do it in 10 minutes. I even had to use a socket and washers for the spacer cause i lost mine. That took the most amount of time.

 

So, did you figure it out???

 

yeah got a new alternator, fixed it... thanx for the help