The Stovebolt Site Forums The Shop Area The Electrical Bay Ballast Resistor location

Been searching like crazy on the web and this site to try and figure out where the ballast resistor should be on our 1955 first series 3600 truck. From what I've been able to tell, it's supposed to be on the firewall, but I don't have anything that looks like a ballast resistor. Is this thing located elsewhere, like under the dash? I can't find anything inline with the ignition coil to act as a resistor.

The truck came with the 6V system and generator, and we're changing it to a 12V alternator system. Our new 12V coil is internally resisted, but I can't find any ballast resistor to remove.

Any thoughts on where the resistor is supposed to be would be appreciated!

They were normally mounted on the firewall on the passenger side fairly high up behind the engine. They had a white ceramic housing with two posts sticking out, one on each end.

none of the 6V systems had a ballast resistor, it didn't start until trucks were all 12V, 2nd series 55s

Bill

With an internal resisted coil no need for a resistor. Turn the key to on, measure volts at coil, 12 volts is good, 6-9 volts and you have a resistor in line.

Ah ha! Thanks Bill and baldeagle! There certainly aren't any that I can see, and it makes sense that there isn't one for the 6V system. It wasn't in the electrical diagrams, so I was scratching my head. I'll probably still check the volts at coil, as you recommend, Steve, but I feel better about it now!

In 56 (maybe late 55), they used the ceramic resistor on the firewall left of center above engine. The stomp starter was equipped with an extra side pole which was hot only while depressing the stomp pedal. It provided 12 volts to the coil (bypassing the resister) during starting to provide a more intense spark. Once the engine was running and the stomp pedal was released, the coil received the 6-9 volts from the resister. If you go with an internal resisted coil, you won't have this unique feature. If you have no problems starting using your internal resisted coil, I wouldn't worry about the switch with the extra pole/external resister deal. I am currently running a 235 with an external resister without the starter switch having the extra pole without any issues with starting.
Carl

Theres a coil bracket that has provision to mount the resister, I use them and they look clean and traditional. It is authentic and original but few people know the difference.

that location on the coil bracket is a provision for the radio noise suppression capacitor, mounting the ignition resistor there will apply more heat to the coil than is desirable

Bill

I put my ballast resistor down on the frame across from the dizzy. There wasn't one originally on my 54. But since I've updated to 12v, and dont have an internally resisted coil, it was the best placement I could think of (looks wise). And plenty of air movement to keep things cool down there.

should be fine if you don't drive in the wet much, but road spray wouldn't be friendly to the coil of resistor wire, which can corrode easily - carry a spare

Bill

I would mount it up on the firewall and use a little rubber washer for a cushion where the screw goes through the mounting tab. That gets it away from the moisture and is less prone to breaking from the vibration of the frame rail.