Alt over charging to 16 volts

[GDR]

So the Wife calls me again( I did the water pump over the 4th). My battery and brake lights are on. Well then get back home quick.

At idle the lights go off. Volts are in the 15's

Rev it up and the light comes on and volts go into the 16's. Put any load on it and the volts drop enough to turn the light off.

For 25 years all I've ever had to do with a alt is put new brushes in. I haven't had any time yet to check into it more. Just looking for any advice before I start digging in the manual.

Its a 91 V6 196k miles. I'm hoping to find a bad connection somewhere not letting the regulator know the real voltage. What do you people think? Will I get lucky?

TIA
Bill

[tr918]

Sounds like the regulator is bad.

Double check to make sure the battery has a full charge and is in good enough condition to hold a charge(won't be the cause of the problem but will interfere with troubleshooting). Do your voltage checks with a known good charged battery. A drained battery will make the lights go out with a large electrical load. If you checked it across the terminals of the battery and it did this you may have a bad/dead battery which is causing the lights to go out. In order to avoid misdiagnosing the problem make sure the battery is charged and then check it again.

If the voltage is high, it is usually the regulator. If the voltage is higher than 13.5 to 14.5volts the regulator is not limiting the current. If the voltage is that high then the alternator is doing its job.

Put a freshly charged battery in and check it both across the battery terminals and across the alternator terminals(alt terminals will be higher than battery if regulator is working). If the volts are still high across the battery replace the regulator. If they are low across the battery check to see if they are low coming out of the Alternator terminals. If they are low across the alt terminals then the Alternator is not doing its job. You can also test the regulator if you have a manual with the specs for the regulator. I don't have my manual with me but it is a resistance(Ohms) check. You can also check the terminals going in and out of the regulator to see what the votage drop is.

Hope this helps.
Good Luck
-TR

[tackepj]

Yeah, definitely sounds like a voltage regulator. Is that built into the alternator or is it a separate piece?

[GDR]

Well the battery is toast. Just sitting over night its down to 9v. Its also 5+ yrs old.
Just broke the + post clamp too. Will have to send the wife out while I read.

I have the manual so I'll check what I can without any power for now.

[tr918]

Is your V6 the 3.0L. If it is the 3.0L it is the same as whats in my T100. I am not sure if the regulator is built into the alternator. Check your manual to make sure. Good luck.

[GDR]

The IC regulator is internal and replaceable. The only check for it in the manual is a voltage check. Too high=replace.

I tried it out with the new battery and clamp. OH Boy! 16.8 Volts. I shut her down quick and went and sat down depressed. I could smell a faint electrical smell from the alt. It was also pretty warm for running about 30 seconds on a cold engine.

I ended up getting Kragens $129.99 lifetime special. Thats the cheapest I found. I could have tried just the regulator for anywhere from $55 to $100 but then the bearings would just go out next week