I'm with Lou. Take it off clean the commutator. I like chucking up in my drill press, spin it slow using a piece of sand paper ( not Emory) hold a strip on the copper. Clean the contact side of the brushes with the sand paper too. You may not need to change them if they are long enough. Makes sure the springs snap down on them.
It just sounds like a resistance problem to me. Does you gen still have the protector ring /shield not. Without it dirt, brush carbon, etc gums it up.
The faster it spins the worse it will work. Short brushes had the same problem.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

It's been a long time since my bird was original, with 6v positive ground. But bear with me. The gen light is hooked between the output and the battery on an alternator. So, if the alt makes more voltage than the battery, it goes off. It also provides the "exciter" circuit to cause the alternator to charge on start up, which is why some 1 wire alternators don't charge until they've been reved, and the residual magnetism "excites" them.

A generator light works the same way, but I don't really remember if it comes off the output or something on the regulator. On old generator cars, the light would glow dim at idle, brighter if the heater or something was on. The lack of output (not to mention increased loads, traffic, cost, etc.) was why they went to the alternators in the first place.

Hopefully, someone here with more DC experience will chime in, my career was with AC. But anything that causes the current flow to go from the generator to the battery will start the light glowing, and eventually, bright. At idle, maybe expected. At speed, with the heater, lights, etc. it's a sign the generator isn't making its full output, or enough for the loads.

When I bought my bird back in 1999, my friend took me up, we put a new battery in, stopped for gas, and made a 70 mile drive home. January, and a forecast of snow, so it was cold and I had the heater on. I told him to go on home when I got off the 405, 10 miles from home. He followed me to the driveway. I asked why and he said "Mike, you couldn't see it, but the tailights where almost out before the voltage regulator kicked in and recharged the battery. I was afraid it wouldn't, and 3 miles after that it the car would quit."
In traffic and lit up roads, I didn't see the headlights going dim. I was busy driving a car that wandered all over and in traffic at 70.

I suspect you have a similar problem, maybe a ground, maybe regulator slightly out of spec. Hopefully someone else will chime in with more info.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

So I'm going to my first car show of the year this weekend, it's going to be in the evening and dark when I'm driving back.

I would love to have something to try to try and get this issue fixed. What is exactly happening electronically/mechanically that makes the GEN light come on? If I understood the operation I would better be able to troubleshoot things.
It doesn't come on in a binary way off one minute on the next. It very very slowly illuminates so soon you don't even realize till it's bright and concerning. That's one of the irritating things about it because when you're expecting it you find yourself paranoid and trying to check the guage because the illumination of the rest of the cluster bleeds through to the gen light and makes it LOOK illuminate so I keep turning my lights off momentarily to check if it's on.

Does this gauge ultimately connect to somewhere on the generator itself, the regulator box, or the battery side of the solenoid?

Re the ammeter mentioned, they are common at swap meets, but It measures current, not Voltage.


Paul

Dang, now I love stories like that. For what I know the ignition switch is still original in my car like most things. Wouldn't be surmised if it's work over 60 years. My car also has a worn neutral safety switch gotta keep shifting into neutral and fiddle with the shifter to get her to start.

Wish I knew more about electrical systems, I have no idea if the ignition switch could do that. Anyone else know? Weird that it'd cause hard starts. Think it maybe limits the power to the plugs if its worn?

Really wish I had an Ammeter for the car but it's hard to find one that goes down to 6v. Plus not sure if I know how to hook it up.

About 30 years ago I had a 54 that did that very thing. Gen light would come on very dim, increasing with engine speed. The car also had hard starting problems and since I suffered from the short patience of youth and wished it to start like new cars, I changed to 12V but instead of alternator I used 12V generator. It cured starting problem and worked fine but still had the odd generator indicator light problem. I sold the car to a gentleman that wanted it original and changed everything back to 6V positive ground. When I asked about the starting problem, he said that he found a malfunctioning ignition switch, and when he replaced it there was no more starting problem or generator light problem. Now, I am merely telling the story for what it's worth, but I wondered if maybe there could be truth there? Could an electrical path form inside a worn ignition switch that allowed this to happen?



Tom from the chiggerfarm located in the beautiful Heart of Central Texas

When you cannot dazzle others with your brilliance, baffle them with bullcorn!

Yes, case is grounded to body and through wire to generator, but I'm not sure how that relates as yours is 6V positive ground. Sorry, it's been too long ago I worked on positive grounds

Doesn't the regulator ground through the case?

The problem is there aren't many, usually just two, battery to block, block to body. I always add extra to body and frame. Then all the components like voltage regulator, lights, accessories, gauges etc depend on a good body ground.

: / I don't even know where all the grounds are..