Generator Light On

[kaferdude]

Ok, here's the issue.
Vehicle: 1949 VW. I recently obtained and installed a 25 hp VW engine which had been in dry storage for about the last 8-10 years (the engine was running good when put into storage). After starting the engine to do some of the carb, timing adjustments, the dash red generator light would eventually go out after about 5 minutes. Over several days, every time I started the car the generator light came on strong (no flickering, fading) and then would go out after about 5 minutes. Yesterday, for the first time, I took the car out for a test drive. Light was on for about five minutes and then turned off (as usual). But after about 10 miles, the light came back on and stayed on. Tonight, I changed out the D-regulator with a spare one I had but the light is still on. Checked the generator brushes and one was worn down by about 1/4" so I replaced it. Put a little sandpaper to the commutator and shined it up nice. But the dash generator light still stays on with the engine running.

Any thoughts on what to check next? Really hate to pull the generator for a possible rebuilt if I'm not sure that's the problem. Thanks.

Dan

[bowtiebug]

i would try re polarizing the generator , do a search you will find info
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[johnshenry]

Actually, polarizing the gen will not solve that. If the light goes off, even for a few seconds, the gen is producing power with the right polarity.

Few things come to mind Dan. First, make sure that your dash pod bulb socket has a good contact. Is it snug in the pod, the little finger presses on it fairly tightly? Good metal to metal contact? The gen light bulb is tied to 6 volts on the socket base/pod contact. The wire to the regulator down back is actually tied to the regulated generator out put. It is a bit counter intuitive. Gen not turning or generating power, the screw terminal on the bulb is at 0 volts, the other side of the bulb is tied to 6 volts = bulb on.

Gen spins up, regulator regulates, the screw term is at 6 volts, other side of the bulb is tied to 6 volts = bulb off.

First, get an alligator clip lead, clip it to the screw term on the bulb socket and ground it somewhere behind the dash. Turn the ignition on, bulb should light. Wiggle the bulb in the pod see if it flickers.

Another easy test to determine bulb/vs gen/reg problem: Clip lead a voltmeter to ground and to the bulb socket screw term, drive around a bit, watch the voltage. If it drops off, light goes on, you have a gen/reg problem. If it stays up while the bulb comes on, you have a bulb socket/contact problem. Not likely to be a problem with the main harness wire, unless that wire gets ground somehow, the light will not come on. That is, if it is broken/open, the light will not come on. However if insulation is worn somewhere and it get grounded to the body, it will (??)

If it is not the bulb/contact issue, next thing I would do is check the gen output without the reg. Pull the reg, ground the small wire (brown?) off the gen to the case, and put a voltmeter on ground and the thicker output wire coming out of the generator. Start up the engine. You should get something around 20 volts. Do not run the engine for a long time (more than maybe a minute) like this. You are running the gen "wide open" and the field windings will eventually overheat this way.

It is possible that you have 2 bad regs, but not likely.

Barring those checks, I'd want to watch the reg contacts while running the engine with the reg in place, loading the gen by turning on headlights, etc. In the Zarwerks Spy Cam thread, there are some regulator checks/details that you might find useful.

I love to troubleshoot electrical problems ... but not by e-mail. Right now I'm on a 4 hour flight over the midwest somewhere, so I typed all of that to pass time.....
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John Henry

'57 Deluxe
'51 11E Standard Sunroof (PhotoBucket resto pics)