1936 Chrysler charging system question

[Jon Robinson]

Sorry it's been so long since I've been on this board. I'm going through the messages from the last few months, and it looks like I missed some good conversations.

I just bought a 1936 Chrysler Airstream sedan. I live in California, and I drove it home from Wisconsin. It's a great car.

The charging system is over-charging, though, and today, it blew the fuse in the back of the ammeter. I put an ohm meter on the fuse cup, and there's no short. The car still ran because the ignition system has circuit and fuses of its own, but all the lighting is out.

When I first left Wisconsin, the system was charging all the time at about 15 amps. This seems a little excessive to me, but then again, I'm used to the 1940s-'50s regulator systems which were quite a bit more sophistcated. I don't know anything about these earlier regulators or the three-brush generators.

I have a factory manual, but it doesn't go into the kind of detail you'd think it should. These regulators are simpler than the ones from the 1940s. In the '40s and '50s, the regulator had a voltage regulator for low-load situations, and when the load was higher -- like when you turn the headlights on -- the current regulator would kick in. If I understand the 1936 regulation system, it looks more like the regulator is a voltage regulator only, and you adjust the output of the generator by adjusting the position of the third brush.

By the time I got to California with the car, the charging system was blasting away at a full 20 amps all the time, and the fuse behind the ammeter would get really hot. I would turn the headlights on to divert the current from the ammeter, and the ammeter fuse would cool off. To day, the fuse blew.

I realize the 1936 regulator isn't as precise as the 1940s systems, but it still seems like there should be some response to load. It would make sense if the system charged at 5-10 amps all the time, but not 20, and it would respond to the load to meet it, rather than just being at full blast all the time.

If this were a 1940s system, I would know the generator field coils were shorted out either in the generator or in the charging system, but I don't know if the same holds true on the 1936 three-brush generator.

Any ideas?

JON

[Rusty_OToole]

In the 3 brush generator the 3d brush regulates the voltage. You can adjust it lower for long hiway trips, higher for in town driving. Evidently yours was adjusted way up so the battery wouldn't go dead with lots of short low speed in town trips.

You don't have a regulator just a cutout to diconnect the generator from the circuit when it isn't charging. This is to stop the battery from dichaging thru the generator.

If you peek inside the generator you should see the 3d brush. It is probably all the way to the end if its adjustment. You might try adjusting it, experiment around until it charges right for your use. Or maybe you can find an old time mechanic who knows how to adjust it for you.

[Jon Robinson]

Thank you, Rusty.

Let me see if I understand this. I know well the difference between voltage and current (or amperage, in slang terms). You're saying the position of the third brush regulates voltage, but does it also reglate current?

The ammeter doesn't register voltage, of course. Will adjusting the position of the third brush bring down the current?

It's charging at a full 20 amps, and it blew the 20-amp fuse. The reason I'm asking about this is that, at the moment, when I turn the headlights on, the amperage drops to just above zero while driving, and the lights are nice and bright. If I adjust the third brush for less amperage, will the generator keep up with the load of the lights, or will the ammeter drop to the discharge side of zero and give me dim lights?

My 1934-'36 factory manual does have diagrams and schematics, but they're really weak on labeling the parts in the diagrams and equally as weak on diagnostic procedures. They probably had separate books for the electrical details.

I don't see an external way to adjust the position of the third brush. Do I have to pull the generator? I don't mind that at all, but I'd like to be sure first.

Do you know of a source for generator brush sets that include the third brush? The third brush is thinner than the others.

JON

[Jon Robinson]

Here's an attached photo of the '36 Chrysler if you're curious.

JON

[Rusty_OToole]

The 3d brush regulates output. The cutout regulates voltage. You can reduce the output of the generator which is what you need, by adjusting the 3d brush. This is a simple adjustment done on the car. Take the cover band off the generator and peek inside. You should see one brush is moveable. I'll bet it is rammed as far as it can go one way. That's why it is charging so hard. No doubt it was set that way because the last owner puttered around town at 20 MPH and never went more than 2 miles at a time. So the mechanic set it high because his battery was always going dead.

There are ways of adjusting it that should be in your manual but if not try backing it off and see what happens. If your battery doesn't charge, push it up. If it boils dry push it down.

I suppose your cutout could be stuck too but in that case I think you would know it.

[Jon Robinson]

Rusty:

I work for NAPA Auto Parts, and I picked up some 20-amp fuses for the ammeter, instlled one, and everything came back on. Then, it was time to work on the generator.

I pulled the generator, and moved the third brush closer to the nearest main brush as the manual indicates. I made a big changes because I wanted to see what it did. I fired up the car, and I had nothing. I found the fuse in the cutout relay blown also, so I'll pck up some of those today.

I took the cover off the regulator, and I set a rubber hammer on the cutout relay to close the points and fired up the engine again. When the engine is off, and I turn on the headlights, and ammeter will drop to a 20-amp discharge, but with the engine on, it only drops to about a 10-amp discharge -- meaning the generator is working, but I now have the third brush set at too low an output, which is OK because I'm learning. I'll install the cutout relay fuse tonight, and move the third brush again.

I have a concern. This car has a sealed-beam headlight conversion from the 1940s, and I suspect the sealed-beam headlights take a lot more current than the original bulbs. Maybe some previous owner greatly increased the output of the generator to keep up with the sealed-beam lights, but it's too much current when the lights are off. I'm concerned that if I drop the generator output to only, say, 10 amps, it won't be enough to run the lights when I turn them on.

I'm in the market for an original set of headlight reflectors and bulb sockets. I'm also investigating six-volt halogen bulbs. Maybe, I'll be able to drop the generator output with a proper set of lights in the car.

I was looking at a 1949 "Motor's" manual last night, which goes back to '36, but the information is a little vague because those cars were so old by 1949. Apparently, Chrysler converter to the much better voltage/current regulator I'm used to on the '40s cars in 1937. I sure wish they had done it one year earlier. I did have the thought of installing the 1940s system, but the connections on the ammeter and the wiring of the rest of the car is different enough that I don't think I can do it safely. I'd rather have the original equipment working properly anyway.

I'll let you know what happens tonight. Thanks for your help so far.

JON

[bebop138]

Jon, love the car!!! Check your PM`S----Lee

[Guest imported_Terry kean]

Jon, With the third brush setup you will not find a perfect one setting for all driving conditions. If I am going to be driving at high speed during the day on long trips, I adjust for a lower charging rate. Running with the lights on at night for long periods will require a higher setting. At times I just leave the headlights on to avoid overcharging during the day. Your trip to the coast was probably mostly daytime driving with minimal brake light use which required the least current requirements. As you probably already found out, the third brush adjustment is very simple so it is not really as bad as you first thought. Good luck, you have a beautiful car. Terry

[Rusty_OToole]

Now you know why they changed to the more sophisticated, but more expensive voltage regulator. Your system gives a constant charge that does not vary with load. Sometimes it charges too much, sometimes too little. You have to set it for "average" conditions. Puttering around town, shove it up. Going on a long trip, shove it down. A little old lady would need a different setting from a travelling salesman.

The only thing you can do is set it for "average" conditions.

One thing you can do today that they couldn't do in 1937 is bleed off excess voltage with a zener diode. English motorcycles used to use an unregulated alternator - wide open all the time - and bleed off excess voltage this way. You need a zener diode and a heat sink to do this, that's all.

[Jon Robinson]

Rusty, Terry:

I got the 6-amp fuses for the cutout relay, and fired up the engine. I was surprised to find that the adjustment I made the night before didn't make any difference.

Picture this: The nearest main brush is on one commutator bar, and we'll call that Bar Number One. When I pulled the generator, the third brust was on Bar Number Four, meaning there were two full bars between the main and third brushes.

The night before, I adjusted to where the third brush was on Bar Number Three -- one full bar closer to the main brush which the manual says is the direction for decreasing current. It made no difference, so last night, I adjusted it to where the third brush is on Bar Number Two -- the next bar -- and it still made no difference.

Without the headlights on, the generator is blasting away at the battery at 20 amps. I checked the voltage regulator, and it's doing its job perfectly at all RPMs.

Am I not making a big enough difference in the third brush adjustment? Should I move the third brush to where it's nearly touching the next main? Terry, when you adjust yours, how much difference does it make to adjust the third brush one full commutator bar?

I live on a lot of open road, and I take a lot of trips. I drive with my headlights on a lot on two-lane roads no matter what I'm driving just to be seen easily, so I don't mind driving the Chrysler with the headlights on a lot of the time. When I go into I can turn them off, and when I'm on a big-city freeway I can have them off, too, but for a different reason. The previous owner did a nice, neat job of installing a set of unobtrusive turn signals. They're small but bright, and you don't really notice them until they start blinking. I'm glad to have them, but as usual with generator systems, they do get a little dim and slow when the headlights are on, which is no big deal at night, but during the day, the dimming could make them less visible with all the sunlight. Putting around town, will be fun, but on a big, multi-lane freeway, I would not want to drive with the headlights on because I'd want the turn signals nice and bright for lane-changes, and that's where I think the battery will take a beating.

JON

[Rusty_OToole]

You've got me there. The only 3 brush generator model I ever owned was a 1947 Indian Chief motorcycle and it responded to moving the brush.

All I can suggest is you try to find an old time auto electric repairman. I would try to help but from this distance there isn't much I can do.

[junkyardjeff]

Wiring a newer generator and regulator might be easy if you are not concerned about 100 percent originallity. Jeff

[Guest De Soto Frank]

Jon,

If you did want to "upgrade" to the 1940's-'50s MoPar three-element regulator generator set-up, it shouldn't be too hard...

Besides getting the compatible genny/ regulator, you would need to make a new sub-harness to go between the genny and regualtor, but once that's done, you simply need to have one wire that runs from the "new" regualtor "Battery" terminal to the "Ignition" side of the Ammeter, or similar "load-side" of the ammeter.

Your now-abandoned stock wires could be taped-over and "abandonded in place"...

I think Rusty made some good points about the old 3-rd brush system having some inherent limitations, which may render it unsuitable for our (modern) driving habits ?

( Not saying you shouldn't try to make your OEM system work as the factory intended, just proposing an alternative...)

[34 Dodge]

Jon,

There are at least two companies who will convert your old generator case to carry an internal alternator putting out about 50 amps. The "genernator" will then look absolutely original and will provide all the advantages of an alternator. If you're interested, contact me and I'll look up the manufacturer's information for you.

Ken Sobel

hypnotist01@sbcglobal.net

[Jon Robinson]

Ken:

I unfortunately really like the idea of the alternator hidden inside the original generator housing -- "unfortunately" because I really like to have all the original equipment working. I have a feeling I'll wind up making this conversion.

I probably wouldn't be so quick to consider the conversion if the generator actually responded to the adjustments. Even when I've moved the adjuster a long way, it doesn't make any difference in the over-charging situation, and it forces me to drive with the headlights on all the time. If the adjustments made a different, I'd probably stick with the original system.

Please post the conversion-maker's information, and I'll look into it.

Frank, I've rewired the 1940s generator systems several times, and I know I could wire up a post-1937 system into this car, but I'm a little concerned about the wiring of the rest of the car. Looking at the schematics and at the ammeter itself, I have the feeling I would have to rewire other components to make it work, and I'd rather not do that.

Thanks you all for your suggestions, and I'll let you know what happens. I'm going to try the generator adjustment one more time, and make a decision about the hidden alternator conversion.

JON

[Guest DougD]

Jon,

Here's some thoughts on your overcharging problem. I'm not sure that they lead to any one conclusion, but perhaps will provide a clue.

1. In a 3rd brush + voltage regulator system, it's the voltage regulator unit, not the 3rd brush, that is supposed to prevent overcharging of a fully charged battery. The voltage regulator does this by cutting resistance into the generator field circuit when the voltage reaches the fully charged level. The 3rd brush adjustment is used only to limit the output current of the generator to its rated capability, 21 amps for your 1936 model generator, when charging a fully discharged battery. The 3rd brush doesn't have to be adjusted for "average" driving conditions when voltage regulation is provided. Instead the brush is adjusted to limit the output current to 21 amps with the voltage regulator bypassed. When the voltage regulator is active, it may be difficult to see any effect of the 3rd brush since the VR unit is already reducing the field current.

2. The current regulator in the later 3-unit regulators basically has the same purpose as the 3rd brush: to limit the output current to a value that doesn't overload the generator. The advantage of the current regulator over the 3rd brush scheme is that it doesn't reduce the generator output at low speeds. The current regulator only comes into operation when the output current actually reaches the rated capability of the generator.

3. In your first posting, you mentioned that the fuse in the regulator was blown and, later, you reported that you had replaced the fuse. Since the fuse is in the generator field circuit, it seems odd that the generator worked at all without the fuse. Is it possible that someone bypassed the fuse or grounded the generator field terminal to get the generator working? Or could there be an inadvertant ground on the field in the wiring or internal to the generator? Either of these would prevent the VR unit from properly reducing the generator output even though the VR relay was opening its contacts. Does the generator stop working if the field wire from the generator is disconnected from the regulator?

4. You mentioned that the VR unit seems to be working properly. Have you been able to determine that the VR unit actually reduces the generator output current when its contacts open or just that the VR unit relay operates when the voltage is high? The generator current should drop substantially when the VR contacts open and cut the resistance into the field circuit.

Doug

[34 Dodge]

Go to www.gener-nator.com for information on the company that converts your generator housing into an alternator. The guy lectured at the Dodge Brothers National Meet a year ago. He builds the alternator completely inside your generator housing. It's a single-wire connection to the battery. You could run the wire through your voltage regulator (bypassing the old regulator innards) and connect the battery wire to the old regulator post. That will provide a totally original look while providing you with a modern, 50-amp trouble-free electrical generating system.

I know that driving my 1934 Dodge in today's Los Angeles stop (and rarely go) traffic would discharge my battery quickly if I relied on the old 21-amp generator.

Good Luck with your project.

Ken Sobel

[Jon Robinson]

Ken:

Thanks for the info on Gener-Nator. I like idea, but I gagged on the $945 price tag for the six-volt conversion. I have the money, but I won't pay that much.

For that kind of money, I'd rather learn how to make the original equipment work properly. The first thing I need to do is educate myself on how this system is supposed to work. I also need to have a truly knowledgable guy check over this generator and regulator to made sure they're actually working. The fact that moving the third brush makes no difference in the current output tells me there might be a problem. On the post-1937, fully regulated systems, if you ground the field coils to the chassis, the generator current output goes full blast, and I'm thinking my Chrysler's field coils might be grounded.

I've met you a couple of times at WPC functions, and I really like your car. The 21-amp system should have been more than enough to charge the battery in city traffic. If anything, from what I'm hearing, over-charging seems to be the more common problem. A couple of my old mentors are now deceased, and I sure wish I could ask them about this. I'm going to ask around to my old-Chrysler buddies and see if one of them has a working 1934-'36 generator I could try on my car to see the difference.

In the meantime, I'll drive with the headlights on while I figure it out.

Thanks for all your suggestions, and if any of you have any ideas, I'd be very interested.

JON

[Tim Wolfe]

Just adjusted my third brush and lowered the charge rate on my car, it was blowing the fuse and charging too high of rate. Took a couple of tries to get it set.