Voltage Too High

[North Coast Cab]

I was getting a very high voltage reading in my car and subsequently fired a couple of the coil packs. At idle it would put out 14-15v and at higher RPM's would peg the gauge at 17v. I changed the voltage regulator and am getting the same thing.
Is the alternator shot?

John

[Joe Bob]

Most likely the regulator....

[rick-l]

gauge bad?

[WERK I]

Depends on the condition of your battery. A weak cell will cause the alternator to charge at a higher rate.

[North Coast Cab]

Battery is fairly new. Voltage regulator has been replaced and I get the same results. 15v while idling and almost 20v under load.

Could somehting be wrong with the alternator causing this?

Could the voltage regulator be wired incorrectly?

[rick-l]

which car is this? Internal or external?

[North Coast Cab]

55amp alternator with external voltage regulator

[North Coast Cab]

I had a Bosch 55amp alternator with an external OEM voltage regulator (Pelican says it's for a Marchal alternator.)

I changed the voltage regulator and I got the same 18+v result.

I changed the alternator to a Marchal 55amp that I had and got the same results again.

Any ideas? Frustrated.

[Joe Bob]

One poster talked about a battery cell being bad. Have you changed out the battery or had it load tested?

[911pcars]

Not sure this helps, but I found this website: Transpo.com. Has lots of alternator, regulator specs.

http://www.transpo.de/Catalog/Car_Fr.htm

Sherwood

[North Coast Cab]

Thanks. I guess I'll try and pick-up a new battery and go down that route.

[Joe Bob]

Personally I like to test things before I replace them....throwing parts at a problem can get pricey.

[304065]

There's only one thing that can cause overcharging, and that is a voltage regulator that's feeding too much current into the rotor. Period.

It's either a wiring problem, in which you could have a direct connection between the battery and the D+/61 terminal on the alternator, causing full-field current regardless of the regulator, or a second defective regulator. You are always supposed to use the same brand of regulator as the alternator because the "set-point" or the voltage fed to the rotor to deliver the correct output voltage is different between manufacturers due to design differences.

Try removing the regulator entirely and see if you still get high voltage.

[WERK I]

You reported in your first post that the charging when to 17 volts-----were there any alternator/battery components replaced before that?
Does your alternator light turn on with the ignition switch in the "on" position? I seem to recall something weird happens to the charging circuit when the bulb burns out. Does anybody else remember?

[Lorenfb]

"You are always supposed to use the same brand of regulator as the alternator because the "set-point" or the voltage fed to the rotor to deliver the correct output voltage is different between manufacturers due to design differences."

Not true. A regulator is a regulator which is just an on/off switch with a sense point and
some hysteresis.

An overvoltage condition with a good regulator can result from an open field diode in the alternator.

[304065]

Loren,

Are you saying it's the sense-point that's different and the voltage fed to the rotor is identical?

Of course it was so important to the Factory to match up the brands that they remind you in the engine compartment.

[Lorenfb]

Regulators just supply whatever the battery voltage is that's supplied to their +B terminal to the
alternator field. Obviously there's variation in each regulator's regulation voltage which is usually about +/- 3% @ 14.0 volts.

[averyhabbott]

Wouldn't you know it, I'm having the same problem, and so is the guy that posted
Inconclusive alternator testing

I'm suspecting battery and/or wiring on mine, for two reasons:

1.) There is slight corrosion buildup around two of the cells on the battery, but none on the rest.

2.) For the last two days, when I start my car, it doesn't start charging. I've had to turn it off, pop the hood, and wiggle the positive cable that runs to the alternator.

For me, hopefully I'll find something if/when I finally remember to check the suspect cells on the batteries. If not, maybe I can fix it by re-stripping and connecting the positive leads running to the battery.

Let me know what you find!

[rick-l]

Originally posted by averyhabbott
Wouldn't you know it, I'm having the same problem, and so is the guy that posted

You really should start a new thread with your problem. This is from last May and the parites are probably not paying attention.

It soundsl like you you have a different problem in that your alternator is not charging (I take it the light is lit). Does your 80 SC have an internal regulator?

Looks like Mr Alternator will be coming out for inspection and rebuild.

[dshepp806]

agree w/ Laurenfb on this one.......not a "brand thing" but more so regulation points...one can match it up...

Best,