Alternator Issues

I have a 1997 Isuzu Rodeo LS. Recently I had the alternator replaced since it was not charging the battery-had to charge the battery to start the car. I bought a used alternator (from a same make/model/year vehicle) and had it installed by a mechanic. After installation it worked for awhile and then the AC/blower quit working, the four-wheel indicator light turned on and so did the battery light. The charging indicator shows over charging (over 12V, possible 16V). I suspect the voltage regulator in the current alternator is bad but I’m not sure. Should I go ahead and replace the alternator again with a rebuilt one?

You need to get a second opinion from another independent mechanic. You may have other problems like bad wiring or a shorted component which is causing a large current draw. A new alternator may fix the problem but I have my doubts. The problem needs to pinpointed first then go from there.

I don’t think a second opinion is in line.

He bought the alternator, and had a mechanic install it.

“After installation it worked for awhile”.

I think he just needs to go back to the mechanic, say that the used one I brought you failed, and could you order me a new one and installit.

Mention the 16 volts and he’ll probably test the system.


Thanks for all the comments. Will have the alternator replaced again and hopefully it will fix the problem. The electrical system worked right before the alternator completely failed and replaced. The charging system is indicating about 14-15 at this time. The blower goes on and off but not too frequently. The A/C light does not come on at all. And it squeaks after it starts–the voltage indicator falls to 12 and below and it stays there until the squeaking stops then it goes to 14/15. It also sounds as if the fan (?) is hitting something when the vehicle accelerates–it also goes away after a few minutes.

Sounds as if your belt is slipping or it could be the automatic tensioner. You could spray the belt with a little water and see if it quiets down. If the belt is slipping, then that could be why it’s not outputting a full 14 volts. Also, what is the age of the battery? Are your battery connections clean. An old battery or dirty connections can stress the alternator.