Electrical problems: lights worked until last year

Electrical issues
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Joined: Sat Jul 14, 2007 1:56 pm

Electrical problems: lights worked until last year


Post by FFMedic » Wed May 28, 2003 2:12 am

The lights all worked until last year when the headlight bulb burnt out.

I have a '48 Pan that my father bought in '49 and he has since passed down. From the manuals I have I see that there is a Generator Cut-out relay. Is this like a regulator? If not (which it does not sound like it is), what is it? I also see that the generator has a charge rate which is adjustable.
My problem...
The lights all worked until last year when the headlight bulb burnt out. (By the way, this is an all original bike, still 6V) Up until now (this year) I have used the spots and the running lights with no problem. I get the new bulb, install it... NOTHING... I check the voltage, 0.5, 0.9.....1.7... etc. Ground, right? Take off headlight, clean all connections, reinstall.... NOTHING, same stuff... Check the high/low beam switch? Sure, pulled it off (sure is packed in that handlebar tube!) One of the wires is showing ware, but can't get to much of the wires to come out, didn't want to chance breaking one! An electrician friend of mine (father-in-law) comes down, checks voltage, 0.5, same as before. Then out of the BLUE, it reads 7+ Volts!! What the? Don't argue, hook it up, QUICK!! Hook it up, start it up, lights on! Bike starts to run like the brown stuff, and the lights are all dim. I realize that 6V run dim at idle, but also dim at high RPM, while it is still running like crap. Turn lights out, runs fine.
Sounds like a short of some sort to me, in handlebar? Electrician is not a biker, and is used to high voltage on machines, so he's not really sure. A biker friend of his says it sounds like a regulator problem (where the first question comes in)... Sorry it's so long, but figured the more information, the better the diagnosis! Any help would be appreciated....

Posts: 158
Joined: Fri Mar 19, 2004 3:35 am
Location: Maine USA

Re: Electrical problems


Post by haggis » Wed May 28, 2003 3:23 am

Hi FFMedic,
First of all that harness has got over 50 years on it, so it could be breaking down anywhere.
Anyway, here's what I would try.Find yourself a meter with an audible continuity test, one that beeps when you join the two leads together.
DISCONNECT THE BATTERY. attatch the black negative lead of the meter to a good ground on the frame then attatch the red positive lead of the meter to the positive terminal of the lamp socket, turn the lamp switch on and move the bars, wiring in the general area etc, if the meter beeps you 've got an intermitant short to ground somewhere.This is where I would start, some of the other members will probally have more ideas, good luck Haggis

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