The Stovebolt Site Forums The Shop Area The Electrical Bay generator question

I hope ya'll can help me with this one, any help will be appreciated. Generator on my truck isn't keeping the battery up. The ammeter shows a slight discharge while the truck is running. I just got this truck a few months ago and the previous owner had a new voltage regulator, generator and wiring harnes put in. When I disconnect the BAT wire from the regulator and strike it against a ground while the engine is running, there's a pretty big spark. Multi-meter shows generator is working but juice isn't going to battery. Also, gas gauge needle jumps below E when the ignition switch is turned on. With the regulator cover off, all three contact points remain closed. Schematic shows wiring correct to regulator. Any help appreciated, Jacques

Did you polarize the generator? Look in the past posts, or use the service manual. Hope this helps.
Dennis

dabond, thank's for the tip! the polarity is ok, and i think the problem may be in the generator,even though it's pretty new. it looks like the truck wasn't driven much lately, so i'll take down the generator and check the brushes and armature next. i'll let you know what i find. thanks again, jacques

http://vernco.com/id569_m.htm#how_to[*]http://vernco.com/id569_m.htm#how_to

I cleaned the commutator and put in new brushes and polarized the gen before starting. Ammeter stil shows slight discharge at all rpms and there's no spark from gen lead to ground when running. Mechanic friends around here are no help, they say, "that truck's so old, the radio only plays French (cajun) music". What should I do next? Also, battery isn't being drained as it would be with a short circuit, it just isn't being charged up. Thanks, Jacques

Generators don't charge at low RPMs. What happens when you get the engine up to about 1500 RPMs? Does the ammeter go positive? If so, everything is normal. If not, I can think of two possibilities; the fan belt is slipping or the generator is bad.

well guys, i'm finally getting closer to solving the dead generator problem. i was about to give up finding out what was wrong and was going to take the gen & regulator to an ignition shop. the guy there said "bring in both of 'em, i'll put them on the tester and i'll see which one you need." thoughts of just replacing either one without finding out what was wrong or what caused the problem kept dancing through my head. i decided to take a look at the regulator one last time. you might remember that i told ya'll it looked brand-new, and that i thought the po must have put it on. well, on the back of the reg are two resistors made in the shape of a coiled wire. the burned to toast. what could have cause this. i'm wondering if the po might have put a 12v battery in by mistake before i got the truck. i know now, i need to replace the regulator but i'd like your thoughts on this so this doesn't happen to the new one. thanks again, jacques

Maybe a 12V jumpstart was in your trucks' past.

Sounds more like a prolonged short to ground. A 12 volt battery or jump start would simply open the circuit in the regulator and stop charging. A reversed circuit jump start probably wouldn't do it, because the generator would have to be charging, meaning the engine would be running. Sounds more like a severe overload, i.e., a dead short.

Well folks, I'm back from the world of electrons, sparks, Ohm's Law and the generator's generating again! The commutator's sentence has been commuted, the regulator's been replaced and is regulating and ammeter needle is pointin' to charge. Thank's for the help in diagnosing this problem. As it turned out, whoever installed the "new" voltage regulator crossed the wires at the generator and that must have been what burned up the resistors on the back of the regulator. Now I'm off to find out why the brakes are broke, or why they don't brake when I want them to. Best regards, Jacques

Brakes? Who worries about them? Good to hear you got the juice flowing again.

speaking of 12v restarts...

if u were to be out in your old truck with the 6v system... and u needed a jump off...

would u need to carry around some cables that woudl step down the 12v to 6 v ?

to keep from breaking things?

Just curious...

I would bet a 12v jump could possibly damage your instruments.. Fifthave would be the expert here. Other than that, it would certainly work, a 6v starter will work on 12v, not indefinitely, and some not very long, but Im sure it would work for a jump. If you really wanted to be careful, I would use alternate wires to start the truck if you were doing a 12v jump. like, use a jumper wire to supply power to the coil, and use a remote starter to start the truck, leaving the keyswitch off untill the truck is running and the booster cables are unhooked, then when its running under its own power, turn on the keyswitch, remove your remote starter and jumper to the coil and you should be set. By using the jumper wires and remote starter, you will avoid damagin your gauges or accessories.

Back in the good old days on the farm when you wanted to jump off an old 6V tractor or combine with a 12V we just hooked a jumper wire to the frame and hit the input wire of the starter with the jumper cable so there wouldn't be any feedback through the regultor or cotout. FOf course the only gauge back then that worked off of electric was the amp gage which wasn't effected anyway and the starters were Autolite which didn't have to have the Bendix pull or pushed in. If you have the bendix pushed in on the starter when you hit it with a light duty 12V battery there should be enough voltage drop from teh battery and jumpers to where there shouldn't be any damage to the regulator as long as you get off of the connection immediately after teh engine starts.

I've jumped mine a couple times by disconnecting a battery cable and using the 12 battery to charge the 6 volt battery for a few minutes. That usually gives enough juice to disconnect the jumpers and hook the battery back up.

These last few replies could go into a new topic, but maybe we can keep it hidden here.

Else, some hawn-yock will start asking questions what'll git us reclassificized as dumb!

Woogeroo started talkin' about jump-starting a 6 volt system with a 12 volt source.

speaking of 12v restarts...

if u were to be out in your old truck with the 6v system... and u needed a jump off...

would u need to carry around some cables that would step down the 12v to 6 v ?

to keep from breaking things?

Just curious...

Well, since you asked.......

I'll tell you what my dad showed me to work around the 6 volt vs. 12 volt problem back when we had a '39 Chevy with a 6 volt and a brand-new Chevy with a 12 volt.

If you think about it, this is the good part about having the old boot-stomper starter on the floor instead of a fancy-modern solenoid drive.


Dad hooked the cables to the battery on the '56. Then, on the 6 volt '39, he attached the positive cable to the stud where the battery cable connected to the starter motor and had me climb in the driver's seat.

He told me to leave the key turned off while I mashed down on the starter pedal. Of course, the battery on the '39 was dead, so nuthin' happened until he touched the negative cable lead to bolt where the starter motor bolted in to the flywheel housing. I had sense enough to hold the clutch down at the same time I was steppin' on the starter, so as soon as he touched the negative cable to the bolt, the '39 spun like a top. And she'd have started, too, if I'd had sense enough to turn the key on.

One more try and the old '39 cranked right up. It was so much fun, I wished he hadn't gone and bought a battery for the '39 right away, but he didn't see the fun in jump-starting the car.

He's gone now, so I suppose I can tell that after him showing me how to jump-start the '39, I used to take his keys whenever I though I could get away with it, and go start the old '39. I never tried to drive it at that age (What a fool I was! I could have driven it up and down the driveway). I always figured I could say I was just trying to keep the battery charged up.