The Stovebolt Site Forums The Shop Area The Electrical Bay Resistor bypass to coil

I have a 54 w/ a 62 235engine, converted to 12volt. I was tracing out the ignition wiring and noticed I have no resistor bypass to the coil. There is only one wire to the coil and it comes from the backside of the resistor on the firewall. Is this unusual? The truck runs fine and starts without fail, knock on wood. Is the bypass necessary? Any input is appricated

Probably not necessary in Florida with a well tuned engine.

You can get by without a resistor bypass, but since the factory chose to include one, my opinion is they wouldn't have made the vehicle with any unnecessary circuits. Do you have a key start or a stomp start system? It's easy to bypass the resistor with the key start setup, just add a wire from the "I" terminal of the starter solenoid to the (+) terminal of the coil. For the stomper, you'll need the starter switch with the small (#10) side terminal, connected the same way.
Jerry

The truck has a key start with a hydramatic trans. I was going to add it however I thought it was odd that the truck started without any trouble. This would mean the coil is getting enough power even with the starter engaged? The only thing holding me back from adding the bypass wire is "if it ain't broken don't mess with it " and my lack of experience.
Thank for the help

IMO: The Ballast resistor was used to reduce the stress on the coil and points after starting truck. It's referred to as a bypass because during start mode, on switch or foot, it, itself, is bypassed and 12V is sent to coil, then upon letting off on sw or foot, voltage goes thru the resistor to the coil. It controls it's own resistance according to the heat, caused by current thru it, and thus, reduces voltage/current to ignition components. Your coil probably says "Use with external resistor". Unless you switch to HEI, it may/will be safer to leave it. They say it also protects a situation of: key left on, points closed.....burn up something. On a key switch with momentary start position, it is bypassed thru the switch/solenoid wiring. On a foot switch,(which is a foot operated solenoid)(get it? sole...noid) it is bypassed with that stud sticking out the side of the foot switch. As Jerry said. I didn't see his last two sentences when I first posted.. Just to be clear, when I speak of bypass, I mean momentarily bypass as designed, not permanently bypass, as in, not using the Ballast Resistor.

I understand that the bypass is only utilized during the strating of the engine. I thought it was needed during starting because the starter draws so much current that ther was enough power left to overcome the resistor. Therefore the bypass was needed during the starting to get adquate power to the coil. If this is true how does my coil get enough current without the Bypass?

The coil primary circuit is wound to function at 100% efficiency at approximately 9 volts, which just happens to be what's available with the starter drawing its full load. The bypass supplies full battery voltage to the coil while the starter is running, then the resistor falls back into the circuit as soon as cranking stops to prevent overcurrent from damaging the points. Starting without the bypass results in the coil working at around 60%-75% efficiency, adequate for most starting needs, but not all. The most likely time the ignition voltage will be inadequate will be very cold starts, or very hot starts- - - -times the starter will be drawing more than normal current and reducing the battery voltage enough to starve the coil for current. Since the starter has far less resistance than the primary winding of the coil, the lion's share of the juice will go that way- - - -resulting in poor or no spark. Bypassing the resistor gives the coil the extra kick needed to assure the plugs get enough spark during hard-start conditions.
Jerry

Rookie: I was thinking you were NOT running thru the resistor, but upon reading again, I think you are saying you ARE ONLY running thru the resistor. Is that correct? My bad. My mis understanding. If that is the case, it could be worse than the opposite, as I believe has been stated. I took my other answer out, Jerry answered your actual question, I did not.

Yes i'm only running through the resistor. As always I got all the info I needed, Thanks for your time.