Help! HEI Control Mod

[rbjbmbtj1]

I have intermittent spark problems. Once my 1975 vette warms up I lose spark. Can the control mod be the problem or is it the coil?

Thanks,
Ron

 

[LLC5]

I have intermittent spark problems. Once my 1975 vette warms up I lose spark. Can the control mod be the problem or is it the coil?

Thanks,
Ron

It could be many things. The visuals you can do are checking the distributer rotor for carbon tracking through the center, visually check the ignition coil by removing it and closely check for carbon tracking and doing an ohm check on the primary side, on a vacuum advance HEI you can disconnect the vacuum hose and plug it then test drive and see if the problem disappears, if it does then then wires to the pick up coil are broken where they enter the pick up coil. You can also pull slightly in the wires entering the pick up coil and see if they are loose. Yes, it could also be the control module but there is no check for it, just process of elimination. Good luck with it.

 

[mr.beachcomber]

Just based upon your original post, I'd suspect the control module is starting to malfunction when subjected to heat soak. It's solid state so unless you have a purpose-built machine to test the module's performance outside the distributor, all you can do is replace the module with a new one.

Jegs makes a pretty good replace module as do several other manufacturers. Just remember to apply the thermal grease supplied with the unit when you install it. Good Luck!