The Stovebolt Site Forums The Shop Area The Electrical Bay generator light?

The generator light come on faintly if I rev the engine in the 58.
At idle it is off.
What could be the cause?

a "generator light" in a 58??? you'll have to elaborate a bit

Bill

Lindsay,

My wild guess would be worn out brushes that are bouncing on the commutator when the engine is revved up.

Stuart

You have dirty contact points on the cutout relay in the regulator. There's just enough resistance across the points that some of the charging current is trying to flow through the idiot light, making it glow slightly. Disconnect the battery wire from the regulator, take the cover off, and use a thin slice of index card stock to rub between the contact points. DO NOT USE EMERY CLOTH! Any abrasive at all will cause the points to stick by setting up roughness on the points. They open and close with a slight wiping action to be self-cleaning, supposedly. The cutout relay is the set of points right behind the Battery terminal, the one with the points open anytime the engine is not running. It won't hurt to burnish the other two sets of points while you're in there, but don't create any scratches on the contacts.
Jerry

Yep, my '58 GMC is different from my '58 Chevy as it has no ammeter. It uses a Gen light instead. I wish they hadn't built it that way.

I cleaned up the points the best I could and it didn't make any difference.
At low speeds it is off and at higher speeds comes on faintly.

Should I be able to see 12v at the reg with the ignition in the off position?

I thought the batt terminal should be live with the ign off.

It reads about 13.2 volts a little bit higher than idle.

The battery terminal on the regulator will be hot all the time, ignition on or off. It will read battery voltage when the engine is not running, and almost the same voltatge as the Armature terminal on the generator after the cutout relay points close. If you attach a low-reading voltmeter (0-2V.) from the armature terminal of the regulator to the Bat. terminal, you will be able to read the voltage drop across the cutout relay points. (Engine running) It should be less than 1/10 volt. If you're losing as much as 1/2 volt or more across the cutout, the excess voltage will try to charge the battery through the idiot light, causing it to glow slightly. It's really just an annoyance, as it won't keep the battery from being charged. I've seen the problem solved by using a slightly higher candlepower bulb in the idiot light, so the small current can flow through the filament without making it glow. The real "no charge" indication will work just as well with the bigger bulb, if you get an actual failure. Normal charging voltage against a fully charged battery should be about 14 to 14.5 volts. With a very low battery, the charging voltage can drop as low as 13 volts, with very high current flow (35+ amps). As the battery builds up, the charge current will drop to less than 10 amps, and the voltage will go above 14. It's really difficult to evaluate a charging system unless you're monitoring voltage and current at the same time.
Jerry

I have no power at the BATT TERM on the reg when the truck is OFF. Where would I look for the problem?

Trace that wire back through the harness, and I'll bet you find that someone has wired it through the ignition switch. That's definitely wrong, as it adds resistance to the charging circuit just as a set of dirty cutout relay points would. Try this: temporarily connect a heavy wire, 10 gauge of so, from the Battery terminal of the regulator to the end of the hot (+) battery cable at the starter. Leave the existing regulator wire disconnected, but don't let it short out to anything. (Tape it if necessary) Run the engine, and see if the voltage is correct, and if the idiot light stops glowing. I'll bet you solve the problem that way. If so, make the modification permanent by taping the heavy wire into the loom, connected that way. Insulate the original Bat. wire, and tape it into the harness for future use as a switched 12V. source if needed.
Jerry

Edit: To anyone who has an ammeter instead of a no charge light- - - - -don't bypass your meter with the above fix. It will keep the ammeter from functioning, and might mess up other electrical functions. The idiot light should continue to work with the above fix, illuminating full brightness anytime the generator is not charging. If it doesn't, better scavenge up an original-equipment wiring diagram and start chasing wires!
Jerry

I found what looks like a factory plug that fell off the ignition switch, a heavy 12 guage wire. That gave me power to the horn relay.
It late and I haven't started it yet. I'll try it tomorrow.
THANKS

Hate to dredge up old posts, but this had SOME of what I was looking for. I'm defiantely doing some wire chasing and cleaning the contacts in my regulator tomorrow. But I'd like to see if anyone has someidea what's up with my beastie.
'56 GMC with a stock outfited 270ci L6.

I drove it to work t'other day. When I hopped in & turned the key I get the usual gen light, then I start it and it goes out, normal as can be.
However, as soon as I get to work and cut the ignition off, the light comes on. I turn the ignition on and it goes out, does same when I turn it off & then to acc. Start engine & it stays out, & comes on again as soon as I cut the engine. I already know this is a bad thing & is gonna eat my battery.
After work it got me home OK, have a powerful battery, but sure enough it drained it over the next day as it sat out front.
Thinkin I have a burnt contact in the regulator, but I'd like some expereinced opinion since I tend to avoid tinkering with voltage regulators when there are other options.

You've probably got a set of cutout relay points sticking, which allows the battery to discharge through the generator armature with the engine stopped. A 12 volt system usually takes out both the generator and regulator when this happens. Sometimes a 6 volt generator survives the experience.

Take the top off the regulator and look for the set of points directly behind the Bat. lead. They should be open with the engine stopped, and they should close as soon as it starts. If they're stuck closed, the battery will discharge itself through the generator. Also look for discolored or melted wire insulation at both the BAT and ARM terminals, all the way to the generator. It's possible you'll also find at least a couple of burned commutator bars on the armature, where the discharge happened with the generator stopped. That's a worst-case scenario.

If the cutout relay points are sticking intermittently, sometimes it's possible to polish them gently with very fine-grit sandpaper, like 600 grit or so, and do a thorough cleaning with lacquer thinner or alcohol, followed by burnishing with clean file card stock. The points open and close with a slight wiping action, so definitely DON"T use a point file. The grooves you leave with a file will guarantee they'll stick. Good luck!
Jerry

Thanks for the reply.
No burnt wires or evidence of overheating. Since I have a 6-pack battery with pretty high cranking amps that would be a good sign.
I didn't get a chance to pop the cover off the reg yet. Did charge the batter so I could move the old beast into the car port. The light was out when I went to start the truck, came on with the ignition, and stayed on while it was running. then off with the ignition.
So at least it's acting like a normal issue now. Just gonna have to fiddle with it today now that I have a day off. Hoping it's a simple matter of replacing the regulator. If the jenny kicked it, I guess I'll look into one of those PowerGEN alternators. Dont really have 400 bones to blow out my hiney, but what the hey, may as well do it right!

OK, tried cleaning the contacts on the reg, & it still sticks once engaged. Managed to find one in stock at local FLAPS (it was even made in the US *gasp!*) and put it in. No joy.
Still have the gen light when running and no change in voltage on my meter while engine is running.

Reading 9 ohms through the armature and 13 ohms through the field. Cant find my book & see if that's any indication of toasted internals.

Did you re-polarize the generator after installing the regulator? The cutout relay points are supposed to close while running- - - -that's what connects the generator to the battery for charging. The points should separate as the engine stops. Polarize the generator by making a momentary connection with a jumper lead from the BAT to the ARM terminals on the regulator. 1/2 second or so is plenty of time to leave it connected. If the generator is OK internally, it should develop about 1/2 volt or so at the ARM terminal when running the engine with the ARM and FLD leads disconnected at the generator.
Jerry

Nope, did not do that.
When I jump the leads from Bat to Arm this is with the engine off?
I'll give it a shot and then try reading it with the leads off as you described. Anything will help at this point as finding a replacement is going to be iffy & I dunno if the crazy lookin old guy that rebuilt this for me is still available. Not fun havin a dead truck!

Polarizing can be done either running or stopped, but I prefer to do it with the engine stopped. Another troubleshooting trick for the generator is to attach a jumper lead from the F terminal to ground with the engine running. The voltage at the ARM terminal should rise without limit as the engine speed is increased. Don't run it much above 15 volts, as high voltage can get rough on light bulbs, points etc. If the generator has residual voltage with the leads disconnected (after polarizing) and the grounded-field voltage goes up, you've got a wiring problem or regulator trouble- - - -the generator is OK.
Jerry

Thanks for the help, seems I may have to suck up the expense tho.
No rain or wind today,was able to get in there and tinker some. Tried the polarizaton routine, got a small spark when I jumpered them for a second, then started the pig up. No charge. I also attempred to jumper it momentarily while it was running with the same result.
Grounded the Field while running with no effect on the voltage readings. So I pulled it out and eyeballed it, read resistance through the armature (dead even all the way around), and can find no sign of damage.
Did finaly get ahold of the mad scientist guy that rebuilt it for me and am taking it to him tomorrow to have him test it.
Also got a used core in the mail today that I may have him rebuild so I have a spare on the shelf. Will be a good idea seein as I had a job today that required me to unload my little truck & trailer by hand. MUCH easier to dump it!

Got it to the mad scientists today, and it is in fact toasted.

E-pay part is good and charges like a champ, but it needs a end cap (broken mount) and a wide belt pulley. Anyone have a wide generator pully hangin around?