The Stovebolt Site Forums The Shop Area The Electrical Bay high voltage

Was driving home today and suddenly my volt meter is reading 18 volts. pulled over and it returned to the 14-15 that it usually reads. Drove the rest of the way home without any more problems. Last summer I put in a new regulator, when I did that I also installed the volt meter because I had some ongoing issues and that seemed a good way to keep an eye on them. When the weather turned cold my voltage seemed to creep up upon starting the truck but always returned to an acceptable level after running it for awhile. this is the second or third time the voltage spike has occurred and it always seems to be when it's colder or when I first start the truck but today I had driven about 100K parked for an hour and a half then drove home. It was maybe five minutes into the return trip when this occurred, and like I said as soon as the revs dropped it was normal again all the way home. what's up with that.

Are we talking about a generator, or an alternator as a power source? Most voltage spikes are the result of sticking regulator points, or occasionally bad grounds. Be sure there is a ground wire from the generator/alternator housing to the regulator base, and rub a piece of index card stock between the regulator points to be sure you don't have oxidation or roughness there. Don't change any spring tension on the points unless you have a very reliable way of checking the charging voltage. DO NOT trust a dash-mounted voltmeter, as most of them are a WAG at best.
Jerry

Truck has a generator. Why is it that it seems to be temperature related? is that just some kind of strange coincidence? Will check points and ground in morning . Thank you.

IIRC, some of the Delco regulators had a temperature-compensating system built into them, but it was to increase the voltage slightly under hot operating temperatures. It's been close to 30 years since I did much work with generator systems on a regular basis, so I'd have to look up the specifics of your system to make an educated guess what's going on. Regulator points open and close several times a second under normal operating conditions, and they have a slight wiping action to help keep the contact surfaces clean. If any roughness develops on the contacts, it's possible for them to stick and cause the voltage to go up until the sticking condition corrects itself.
Jerry

Everything now clean and tight ran the truck for a few minutes and the voltage seemed to hold steady at just over twelve, not as much as it was putting out on a regular basis before(14-15) it was clean. With the heater fan running plus the lights on it drops to 11.25 -11.5 is that about right? Have concerns about not enough power now when i turn on amp and sound system. The truck is stock except for the engine rebuild is it maybe just time to address the 50 year old wiring.

Did you bring the throttle up above just idling? If you didn't I wouldn't be worried, generators normally don't put out much at low RPM.

You'll need at least 13 volts, minimum, even with the accessories on. The normal regulated voltage against a fully-charged battery will be about 14.5 or slightly more. Anything below 13 at as fast idle probably means you're running off the battery, not the generator. Did you try cleaning the regulator points as I suggested, using a piece of file card or something similar?
Jerry

Not working today so I once again tackled the voltage problem. Disconnected everything took out battery,generator and regulator. Cleaned battery terminals cleaned posts cleaned up the grounds for everything. dismantled reg and gen as much as I dared and gave everything a thorough going over. while out I soldered a new ground wire to the housing of the reg. Reassembled everything took it back to the truck and spent an hour cleaning up the connecting terminals for everything, Put it all back together. Fired it up and it now seems to be working as well as it ever did. I think that there was just a lot of crap and corrosion. That coupled with what appears to have been a bad ground and some oxidation on the points seems to have been the problem. First real winter driving the Truck and corrosion builds up quickly. Thanks for the advice. Still think it's time for some new wiring, it sure can't hurt it any.