Jump to content


Ballast Resistor problems


Recommended Posts

I there Z owners, I have isolated a spark issue with my 240Z. It has many, many problems but one at a time right? Okay, so the ballast resistor by the coil. It does show 8 volts across, and there are only two posts where wires run (pos and neg side). I have seen some ballast resistors in pictures from forum members showing a third post in the middle with a mystery wire - whats that all about? Different model of car?

Anyways, like I said my car has very weak spark. It starts just fine (I've read that the start position bypasses the ballast resistor but uses it in run) but sometimes doesn't stay running until I wiggle the resistor.

Also, the screw that the ballast resistor is held on by is not screwed in all the way. Someone tried to tighten it but stripped the head, and it won't move even with vice grips/screwdriver combo.

Is the ballast resistor supposed to be grounded? I ask this because if the car is idling steady, if I pick up the resistor off the metal it rests on the car dies. If I wiggle it, it will sputter and cough. I don't know if it's supposed to be grounded, but there is a metal sheath thats bent around it and thats what holds it to the inner wall. I don't have a picture yet. Its very loose and floppy because of the stripped screw, it will stay running as long as that metal sheath stays in contact with the car. If I lift the resistor, the car coughs and dies.

I have not seen any pictures of the resistor on these forums that looks exactly like mine. Can I bypass this thing but jumpering across the top to posts? Is that safe or am I shorting out +/- in a damaging way?



1970 240z, round tops. 15mmHg@2000rpm, 13.8V@3000rpm

Link to comment
Share on other sites

Well I finally got that old stripped bolt out and took the ballast resistor out to have a closer look. When I flipped it over I laughed - this is the most simple thing ever. It's just a piece of resistance wire between the two connection points - 1.5 ohms from point A to B. I certainly don't need a new one, the thing is as simple as a stone.

I took it apart and cleaned all the contacts as best I could (all very small bits) with sand paper. The metal sheath around it was really close to the wire and it might have been arcing to ground when wiggled. I nixed the metal sheath and isolated the whole thing with some electrical tape. I haven't started it up since the car has no battery right now, but I did make the connections at the ends a lot better because the one side was loose. I'll report back once I get it going.

I found another electrical foible at the left headlight - the ground wire had a giant hole in it, and the actual wire inside was nowhere to be found. Kinda makes me suspect a dead short, but since its a ground wire I doubt it. I'll check continuity with my meter before crimping on a fresh wire.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.