1932 Cadillac 3 brush generator adjustment

[Alex D.]

Trying to get my charging system sorted. Not all that familiar with the 3 brush generators. From what I understand, the third brush is adjusted to increase or decrease the voltage output. As of now while hot and at about 1600 RPM it’s putting out 8.3 volts and 14 Amps. The specs call for 7.7-8.1Volts and 13.5-16.5 Amps at 1600-1800 rpm. I will lower the output to 8v or just under. After pulling the cover band off I noticed something to look like a resistor with a brake in the wire. Hopefully the experts here can explain to me what I am dealing with here?

Thanks, Alex D.

 

[m-mman]

Early generators used 3 brushes and NO regulator. They did not use a VOLTAGE type of regulation but rather they used CURRENT regulation and the battery became the buffer for the entire system.
To change the current flow rate you needed to use a screwdriver to move the third brush within the generator.  

Very crude it meant that your car was either constantly under charging (night driving would kill the battery) or over charging (it would constantly boil the electrolyte and sulfate the plates)  

 

The resistor thing is a thermal regulator device.  No, it should not have that break in the wire. 

Three brush systems lasted into the middle 1930s. My 1929 Cad Town sedan has such a system.  

Turns out that there IS an ingenious, modern, solid state regulator that easily fits into the generator case and can solve all these problems.    It is completely hidden when installed. I installed one on my car and it was quick & easy  

You can read more about the 3 brush problem and how the modern regulator is installed on a 33 Plymouth here:  http://www.ply33.com/Repair/voltreg 


The seller of the miracle device is:
James Peterson
P.O. Box 884
Bend, Oregon 97709
email: jpetersonbend@yahoo.com

If you have a 3 brush system on your car this conversion is a must have.

[Bloo]

@m-mman is on point. You can't set the voltage because there is no voltage regulation. You will find the current in the book is a bench test value, and the generator would probably overheat and throw solder if asked to run that high. 8 amps is about right for most cars. It's too much in the daytime, and not enough at night. A good setting requires some experimenting as driving habits make a huge difference. Ideally you want the battery getting just full as you park it for the evening.

 

A third brush generator can't be run without a battery (or some substitute load) because the voltage will run away with no regulation and burn up the field coil. I can't help but wonder if that happened some time in this cars past. Maybe that little resistor gave it's life to save the field coil. If you can figure out what the resistance value was, maybe you can get some nichrome wire and rewind the resistor.

 

Edited May 16, 2022 by Bloo (see edit history)

[edinmass]

The resistor you are asking about is a thermal shunt. As temperature of the wire increases, resistance increases and thus the amperage produced lowers. I would recommend leaving well enough alone. If you smoke that unit you can spend thousands and down the car for a long period of time. Generator output should be set fairly low as today 99 percent of owners never drive at night. Using modern cut outs and solid state cut outs are a bad idea and they have high failure rates. Keep you water in the battery full. On a 32 Caddy I would set the output at 6-7 amps when hot…….after driving for more than thirty minutes. 

Edited May 16, 2022 by edinmass (see edit history)

[Johan Boltendal]

Alex the spare I have is a NOS measured at 0.002 Ohm . the wire material is a non magnetic , perhaps you can determine from your broken, one what it is. Johan 

[Alex D.]

Thank you all for the replies

 

m-mman; Will plan on rewinding the thermal regulator device. After reading about solid state device, I think I will leave the factory system as is for now.

 

Bloo; “Maybe that little resistor gave it's life to save the field coil.” This may have happened after the engine was rebuilt. Ran it on a test stand before installing with no load on the gen. I just ordered some nichrome wire.

 

Edinmass; I will leave well enough alone as you suggest. Those units are harder to come by and more difficult to remove than what you find on a 33 Plymouth. I will rewind the thermal shunt and try to get the charging amps down.

 

Johan; The broken wire is about .46mm at 26ga. Just ordered some and will rewind to achieve about .002 ohm.

[TerryB]

That 0.002 ohm reading might be hard to measure with much precision.  Counting the number of turns and having the same gauge of wire might be more accurate.

[PartsAncient]

Wow!  All of this is amazing!

[Alex D.]

The Nichrome wire came today, and I ended up remaking the thermal shunt. I used a fiberglass circuit board material rated for 265 degrees.

 

With the engine warm and at a fast idle (750 rpm) I have 5 amps at the gauge and 8.1 volts at the battery.

Warm and at 2000 rpm, I have 10 amps at the gauge and 8.27 volts at the battery. Now with headlights on I am at -4 amps at the gauge.    Most likely won’t be doing any night driving but LED bulbs in the taillights may help some.

 

Any feedback is appreciated.

 

[Grimy]

54 minutes ago, Alex D. said:

The Nichrome wire came today, and I ended up remaking the thermal shunt. I used a fiberglass circuit board material rated for 265 degrees.

 

With the engine warm and at a fast idle (750 rpm) I have 5 amps at the gauge and 8.1 volts at the battery.

Warm and at 2000 rpm, I have 10 amps at the gauge and 8.27 volts at the battery. Now with headlights on I am at -4 amps at the gauge.    Most likely won’t be doing any night driving but LED bulbs in the taillights may help some.

 

Any feedback is appreciated.

 

How much night driving will you be doing, and for how long?

 

In my 8-cyl Pierces I run a pair of Optimas wired in parallel mostly for the longer reserve capacity and the faster cranking speed is just a pleasant bonus.  Some friends run a pair of Optimas but with only one wired up, leaving the other as a replacement in case some substantial night driving pulls the first one down.  The latter requires only a single 1/2 x 9/16 combination wrench and can be done quickly. 

 

If night driving is infrequent, you can turn up the 3rd brush in anticipation of substantial night driving, but you might need to turn on the lights in daytime to avoid cooking the battery while the 3rd brush is turned up

[hook]

You can also use LED headlight bulbs/units that plug right into the regular sockets. These will reduce your load significantly. Snyder's Antique Auto Parts has them.

[Alex D.]

1 hour ago, hook said:

You can also use LED headlight bulbs/units that plug right into the regular sockets

I wish I could! Cadillac and Packard used a 3-filament bulb in 1932. Very difficult to find and expensive. Could exchange sockets and eliminate the passing light.  Tried this with a Quartz Halogen conversion but felt that it drew too many amps. 

[hook]

6 hours ago, Alex D. said:

I wish I could! Cadillac and Packard used a 3-filament bulb in 1932. Very difficult to find and expensive. Could exchange sockets and eliminate the passing light.  Tried this with a Quartz Halogen conversion but felt that it drew too many amps. 

I didn't know that. Thanks for the education.

[Johan Boltendal]

Alex, are you using a gel or an acid battery in your car? Allow me to advice to use the acid one. Have exp. the Optima and that cooked the coil as well as leading to an overheating of the generator. It gave up, to 11 volts from the generator. 

I was explained by an electrical engineer why that was, but forgot. What I do know, after putting the acid one in, I never had the trouble again.

You have no doubt the charging info from the '32 WSM, if not let me know. 

Johan

[Alex D.]

Thanks Johan, your advice is appreciated. The acid battery is what I am using.  I purchase my 6volt batteries at a Tractor Supply store.

[hook]

Opinions and suggestions are like behinds, everyone has one and they usually stink. Here's my suggestion/warning. If you have a master switch, be careful not to ever shut it off or disconnect the battery while the engine is running. As it was said earlier there is no voltage regulation in these 3 brush generators and the generator will just go crazy and burn up everything in your car that happens to be on at the time, Like points, condenser, coil, lights whatever. I've seen it happen on multiple occasions when the owner of a car puts the master switch in the floor and some unsuspecting passenger happens to hit it with their foot. My experience come from Franklin automobile gatherings that have the same Delco generator setup like yours. It really makes for a bad day.