GEN light on when key off, off when key on, *intermittent*

[swatson999]

OK, looking for troubleshooting ideas here for a problem that popped up last night.

When I shut the car off, the GEN light came on. When I turned the key to ON, the light went off. Disconnecting the battery at the negative post with the QD, there were some sparks, so *something* was connected and drawing current. I just couldn't figure out what it might be. Now, here's the weird part. After a while, reconnecting the battery, the light was OFF when the key was off! And using a VM, the generator seemed to be operating properly.

Drove the short distance home, and the same scenario...in the garage, shut off engine, GEN light comes on. D/C battery, a few minutes later, no GEN light when the key is off, comes on when turning the key to ON.

So...any ideas where to start? I looked at the schematic, but I'm just not sure where to start...VR? Shorted wire somewhere that opens when cooled down? ???

TIA!

Steve

[ward 57]

Sounds to me that the points in the voltage regulator are sticking. There are three. You have to remember that when the generator is not turning any feedback from the battery will try to turn it into a motor thus your current draw and sparks when disconnecting the battery. Just taking the cover off and filing the points may take care of the issue. Done while the battery is disconnected of course.
It certainly wouldn't hurt to install a battery disconnect switch on your negative terminal. They are less than $10 and NAPA stocks them and with a twist of the knob you never have to mess with the battery cables on the battery again. Oh re reading your post I didn't realize that's what you meant when you mentioned the 'QD'.

[swatson999]

Sounds to me that the points in the voltage regulator are sticking. There are three. You have to remember that when the generator is not turning any feedback from the battery will try to turn it into a motor thus your current draw and sparks when disconnecting the battery. Just taking the cover off and filing the points may take care of the issue. Done while the battery is disconnected of course.
It certainly wouldn't hurt to install a battery disconnect switch on your negative terminal. They are less than $10 and NAPA stocks them and with a twist of the knob you never have to mess with the battery cables on the battery again. Oh re reading your post I didn't realize that's what you meant when you mentioned the 'QD'.

Thanks. I'll take a look, and I have a spare VR I can try. Also, do you think perhaps it could be the ignition switch, terminal "C" failing? (Yes...QD = Quick Disconnect).

[Rusty57]

I would be more suspicious of the voltage regulator points than the ignition switch.

[swatson999]

I would be more suspicious of the voltage regulator points than the ignition switch.

Winner winner chicken dinner :).

The Batt solenoid on the VR had contact points so badly misaligned that they were contacting only in a single, small spot, thus creating heat which heated the entire post holding the lower contact, which expanded/lengthened, thus not allowing for any room for the upper/moving portion to UN-contact when the solenoid was de-energized. Incredibly shoddy workmanship, I'm surprised it lasted as long as it did. Swapped it out for a new one just to get it working, but I'm not happy with that one...same geometry, but I can either bend the post and arm to make them mate more thoroughly, or put the original one that came with the car back in (removed when we first got the car, trying to solve a charging problem that turned out to be incredibly dirty slip rings on the generator). The original one looks to be better made and a slightly different design, anyway.

Thanks for the pointer! Definitely led me straight to the issue... :)

[ward 57]

I'd go with the original and adjust as needed per the shop manual. As you noticed "they don't make them like they used to'.

[swatson999]

I'd go with the original and adjust as needed per the shop manual. As you noticed "they don't make them like they used to'.

Great minds think alike. Just put the old one back in this morning and it's working fine. The points on the new one are not flat, but convex, resulting in the same tiny point of contact as the failed one, while the original one has points that are dead flat and the entire surfaces are in contact when closed. Much better design.

I should know by now that the NOS stuff tends to be waaaaay better engineered and manufactured than the s**t you can buy today. Hats off to those 1950s engineers and techs at FOMOCO.

[Mfr1003]

Can I bump off this topic seeing that it isn’t that old? I had my voltage regulator redone, and aim still getting that stupid red GEN light. It will not go away at all unless I disconnect the battery. I was willing to stick with your Voltage Regulator theory if I Didn’t just have that replaced last week professionally. Any other options?

[Mfr1003]

I would be more suspicious of the voltage regulator points than the ignition switch.

Winner winner chicken dinner :).

The Batt solenoid on the VR had contact points so badly misaligned that they were contacting only in a single, small spot, thus creating heat which heated the entire post holding the lower contact, which expanded/lengthened, thus not allowing for any room for the upper/moving portion to UN-contact when the solenoid was de-energized. Incredibly shoddy workmanship, I'm surprised it lasted as long as it did. Swapped it out for a new one just to get it working, but I'm not happy with that one...same geometry, but I can either bend the post and arm to make them mate more thoroughly, or put the original one that came with the car back in (removed when we first got the car, trying to solve a charging problem that turned out to be incredibly dirty slip rings on the generator). The original one looks to be better made and a slightly different design, anyway.

Thanks for the pointer! Definitely led me straight to the issue... :)

Anyone got picture examples of this condition, so a 4 year old creeping on your topic can understanding? Asking for a friend of course…

I’m the friend.

[swatson999]

I may have a picture around that I can post, but the simple answer is to imagine to convex surfaces meeting in a single point, instead of two flat surfaces meeting across the entire surface area. That single point of contact gets HOT, and the heat causes the supporting arms, posts, etc., on the spring to expand, and thus preventing the two points from physically being able to separate when the contactor is de-energized.

I'll look for pics.

Oh, and "professionally installed"? I'm guessing that means the mechanic simply pulled one box off and put another one on?

OK, here you go. Points when open, then when closed. Notice the tiny point of contact. This causes the heat, which causes the vertical post on the left to expand, which forces the points closed until power to the electromagnet is removed and the thing cools off.

ETA: Not the spring...I misspoke...should have said the fixed post on the left in the pics. It got so hot you couldn't touch it, discolored the metal, and expanded vertically enough to cause the spring to be unable to break the contact (which kept current flowing through it, and it got hotter, and expanded more, etc.). Bad.

[Rusty57]

Thanks for sharing those pictures. They unfortunately are an accurate reflection on the level of quality control I frequently see on replacement/reproduction parts.

I agree that the limited area of contact will produce overheating due to the amperage levels trying to pass through those points. The analogy is using an 18 gauge wire when you really need 10 gauge.

[ward 57]

When digging into the shop manual the temperature is an important consideration of operation. An interesting electrical/mechanical device. I do understand the transition to alternators when they were developed but then I'm 'old school' and stick with the original generator set-up.

[Rusty57]

Thanks for the reminder about operating temperature when checking/adjusting a regulator.

I currently don’t have access to my ‘57 shop manual. I know that for other classic cars I have worked on the instructions for adjusting a regulator include making the final checks wth the cover installed. There were statements to do this because the metal cover changes the magnetic fields around the coils.

That was for Delco-Remy voltage regulators. Not sure if the same thinking is applicable to Autolite regulators.

[Jimntempe]

I recall from the shop manual that it did say to install the cover to check the final adjustment. That was what I recalled. But I went and actually looked. From what the manual says, the only adjustment for which they want you to VERIFY the final numbers is for the Voltage LIMIT adjustment. For that one you're supposed to put the cover on and check and if out of range readjust and recheck. For the others, Voltage cut-in and current limit, it just says adjust it and leaves it at that, nothing about rechecking with the cover on. One might presume that they have determined those other settings aren't particularly sensitive to the cover influencing them.

To anyone with a generator wondering if these adjustments are worth worrying about, my experience is the voltage limit setting is very important. I thought mine was "close enough" since it generally was 13 to 13.8 when running down the road. Yet the battery would slowly discharge over a month of once or twice a week driving and I'd have to put it on the charger/maintainer. I adjusted the voltage limit to as high as allowed, about 14.8 and no longer have any battery issues. At Idle it will drop to 12.4 if I have the AC on. At 1500 it will be somewhere between 13.9 and 14.2 with the AC on. With not much of anything on it will bump up to the 14.8. If it's not at 12.8 or higher, it's probably not charging the battery.

[ward 57]

Good to know. I was wondering why I also had to put it on the charger occasionally. My trips are usually only 5-10 miles.