Guys,

I replaced the Ballast Resistor in my son's Demon at the beginning of summer. He drove it a few times prior to going back to college. I tried to move it today and it wouldn't start. It did the typical roll over and then shudder when I turned it off. I jumped the ballast resistor and it started right up.

I moved the car, shut it off, and tried to start it again. Started right up. What could be causing this? I thought resistor's were either work or fail, not intermittent. Any advice on troubleshooting?

Thanks!!
Randy

Take off and look at it, it is a winding that could have an opening that is still touching off, and on.

Test out your theory.
Put an ohm meter across the resister and then jiggle things to be sure there's no loose connection.

Next possibility I'd test for is loose or oxidized connections. I suspect this more likely. Either at the connectors attaching to the ballast or in the start switch.
Why do I suspect this - because think about how it works. In Start, Ignition 2 wire sends power to the coil side of the ballast resistor. So in Start, the engine should have fired. Jumping it in start would not bypass the resistor. Only when the key was released to Run position would the jumper be carrying electricity.

Ballasts are bypassed in start

I'm thinking loose connetion that got "jiggled" when you jumpered it

Check the bulkhead connector for burnt terminals.

I had one years ago go bad on my '71 Charger. It was intermittent. It's such a cheap part, just replace it & see if the problem is solved.

next time it wont start, pull the yellow wire off of the "ign" terminal to disable the starter & have a helper hold the key to "crank" & you with your meter or a test light see if the coil positive primary terminal & the blue/yellow ECU terminal are being fed & work upstream from them to find the open. In the meantime as said I would clean/wiggle all pertinent connections/terminals starting with the ballast & pull & put back in place the bulkhead which alot of times is enough to restore continuity there. short version: if all you touched/wiggled is the ballast then as said check its terminal connections & replace it. EDIT In fact what I think I would do is bypass it & see if it will start a half dozen times right in a row & dont let it run more than several seconds each time.

Thanks guys! Gonna do some troubleshooting on it today.

Check the integrity of your wiring...'

And make sure the grounds are tight, clean, and over bare metal...


Ain't never lost a ballast in over 20 years of road time...