I have a 95 z28 and think I am having a problem with the alternator putting out too much voltage. I used a multimeter and it is putting out anywhere from 16.6 to 17.3 volts. I replaced the alternator and tried a different battery but it is still happening. Anyone have any idea why this is or is that normal?

 

Start by checking your electrical connections and also see if you have the same voltage across the battery that you do at the alternator. Maybe there is a problem with your sense wire making the alternator put out more than it should. Maybe you can run a temporary sense wire straight from the battery (+). Also make sure you aren't missing any ground straps - you could make a ground wire from the alternator to the battery (-) just for troubleshooting purposes and see if that helps.

 

That voltage level is not normal(around 13.7-14VDC should be max). What is the voltage at the battery with the engine off?

 

I'm not sure what on earth could be causing an overvoltage unless you have another bad alternator. Could you have it checked for proper operation at Autozone(let them spin it up in that tester they have...)?

The small wire with the plug to the back of the alternator...is it in good condition? The main positive wire to the lug on the back is connected, correct? As Kevin mentioned, make sure that it goes back to the battery and is in good condition.

 

When I have checked the battery it has been anywhere from 12.5 to 14.5 with the car off. I did bring the alternator to autozone and they said that it was working properly. The original wire that when from the battery to the alternator was broken so I had to put a new one on there but it seems to be making good contact. I do get the same reading if I test the voltage right on the alternator and across the battery terminals.

 

How about the connector on the bottom/back of the alternator? Is that wire/connector in good shape?

 

Funny how the GM shop manual says a battery voltage above 16 volts, the alternator is defective and should be repaired or replaced. NOTHING else is mentioned. Period.

Prior to you doing all this, did you have a problem? In other words, why did you start checking?

You did check your meter for accuracy didn't you?

 

You should run it down to parts store near by, that tests the electrical system for free while its running in the parking lot. Like stated, make sure you tester is working correctly.

 

In my experience, those tests they run on alternators haven't been all that accurate. A couple years ago I had O'Reilly's check my alternator because it wasn't charging. They said there was nothing wrong with it, but when I replaced it with a brand new one, the car ran great again.

 

I started checking because I was having a problem with my Sub Amp. It was going into protect mode so I decided to check the voltage. I did not check to see if my meter was accurate but it has seemed to be correct in the past.

What is the wire on the bottom of the alternator for and where does it go?

 

Brought the alternator to O'Reilly today. It passed their test. Their computer said it was putting out 14.8 volts. Cleaned the posts and connectors on the alternator and battery and the voltage when up to 17.8 volts.

Does that wire the goes into the plug have anything to do with voltage control? Where does it connect? should I replace it?