i have a 80 model pickup that has started overcharging. its charging at 17-18volts at idle. i have put a new alt and regulator and its still overcharging. any ideas of what is wrong and or what to check to fix. has brand new optima blue top and dont wanna mess it up.

 

did it start over charging so you put the alt in, or did you put the alt and regulator in and then it started over charging

 

Stock Toyota alt.' don't put out until off idel, around 1,2000 rpm's.
And most all systems if the battery is @ full charge 12.5-13.5 volts, the out put shunts to ground.
Lest this is to my best understanding!

 

no, alts put out 14 at idle, some drop down to 13ish if the battery is fully charged, but even our yotas put out more then 12 at idle. 17 is way too high. im waiting for the op to clarify what order his problem acted up in.

 

well the truck started not charging so i installed a new alt. it did fine for about a month then the charge light came on yet when i checked the voltage it was overcharging. was told it was the regulator so i replaced it. but it made no difference still overcharging.

 

As I understand Alternators to function, the voltage output id determined by regulating the input to the field coils. If there is an internal fault in the alternator, then it may be 'full fielding' despite the regulators attempt to reduce input to the field coils.

The gist of all this is...as much as it sucks, you're probably looking at replacing the alternator again. Do you have any friends nearby that could loan you a 'known good' alternator to swap in for diagnostic purposes?

 

no ive got a few but they are from newer yotas and have a built in regulator. it has a external regulator. but i got the new one thats on it from oreillys and i know just about everyone that works there so ill just take it back. and ill get it checked while im there to find out. thanks

 

so i took the "new" alt back had it tested.... and it was BAD!!!! so got another one and so far so good. thanks for the help guys