Another Autolite question for ELECTRO

Crazy Horse · Sep 16, 2019

You replied a few days back to a post I had made here on Tractor Talk regarding my Autolite generator and regulator (current regulator I think). You mentioned that the outside carbon "brick" resistor on the regulator had an approximate 3 ohm resistance value. Here's your reply ....

"For the regulator in your first link the fuse should be a 5 amp fuse and the resistor is 2.85 ohms."

Sounds to me that you know what you're talking about. Here's my question ... How do you know (or where did you get the info) that the resistance value of that resistor block is about 3 ohms? If you reply, I will tell you the reason why I ask this question.

Looking forward to your reply .... Crazy Horse

Janicholson · Sep 16, 2019

A 3 ohm resistor in the field circuit will drop the charging current to a little less than 1/2. That charge rate is really a maintenance level to keep it charged up. The points in the tower pulse to create higher than that charge rate when the battery has been used some. Auto Electrical systems and diagnostics from George Whitehouse, Instructor at Vincennes University 1969. Jim

Crazy Horse · Sep 16, 2019

Thanks Jim. Here's why I ask. The original carbon block resistor was broken at some time in the past, actually about 1/4 of it was attached to one of the outside terminals on the regulator, and a second 1/4 attached to the to the other outside terminal. The center section (about 1/2 of the block) was/is missing. So I removed the anchor screws for the two pieces that were still attached and checked their resistance separately and away from the regulator with a digital ohm meter. Placing the probes at either end of either of the two broken pieces I get a resistance reading of anywhere from 12 to 20 ohms (depending on where I place the meter's probes .... or how close the probes are to each other on the carbon block when I make my reading). I am wondering how that is even possible if a full block is supposed to have a resistance of only 3 ohms.

I hope this makes sense with my description and that you can follow it. Looking forward to your reply ..... off to bed, will read it in the morning.

Thanks for the help with this. I suspect I will reply to your next reply.

Crazy Horse · Sep 17, 2019

Hello again Jim. More info from a web search and from an Autolite manual. This is found on page 45 (Relays and Regulators) of the link below. Here's the chart info I am referring to ...

Model TC4324A (my generator model): REGULATOR SPECS = 6 volts with a 2.85 ohm resistor and a 5 amp fuse.

This confirms what you said in your reply (3 ohms for the resistor) and what Electro said earlier (2.85 ohms resistance with a 5 amp fuse). I don't think those carbon block resistors are available anymore but there are more modern ceramic block encapsuled resistors of all sorts that a guy can use. I have used them in the past on the old 3-position light switch control on some of the earlier generators I have used with just a cut-out relay and no current control tower in the regulator unit.
Autolite Manual ..... see chart page 45

electro · Sep 17, 2019

I got the information from an old Autolite manual, likely the same one you saw.

It is hard or impossible to get the original resistance from a broken carbon resistor. Measuring with a thin probe tip at one small point will give a higher resistance than the real resistance which is over a much larger, broken, area. That method will work with a wire wound resistor but not a carbon resistor.

I have used the ceramic sand covered wire wound resistors for this type of application. At least 30 watt in size.

The resistance is not critical, a 3 ohm should work.

The Autolite two charge regulators, like what you have, work differently than the standard vibrating regulators. The resistors are a good bit lower in resistance than what you may be used to seeing with the standard regulators.

Since it is used with a 3 brush generator, protecting the output from overload is not needed since they are self limiting. The field current is not self limiting which is the reason for the 5 amp fuse in the field circuit.

Janicholson · Sep 17, 2019

The more material touching each end (screw/clamp) the less resistance. Contacting with a meter lead will not do it. Jim

Another Autolite question for ELECTRO

Crazy Horse

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Janicholson

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Crazy Horse

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Crazy Horse

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electro

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Janicholson

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