The Stovebolt Site Forums The Shop Area The Electrical Bay HEI Electrical Problem?

I have a perplexing problem with my '42 PU...it has a 235 w/ 12V generator & starter...plus a GM Mini HEI and an 12V coil. The truck ran fine for couple of months...during the last NE coldspell it sat for a week (inside garage) after that week I started it up and it ran for a few seconds and stalled. I've was unable to restart it. We troubleshot the problem and the truck was getting power through the coil. We thought we had a major flooding problem...but after careful remediation we found that was not the case. We moved on to other potential causes...lo and behold we found that the HEI module in the distributor had failed.(It like nearly everything on the truck was new)...What could have caused this failure? and how do I prevent it from happening again?

steveg,

Is the HEI unit actually a GM unit and does it call for a specific coil just for that unit. The modules can and do fail..have you crossed paths with a black cat recently?

Stuart

Stuart...good question on the coil...the GM HEI (from Tom Langdon) did initially come with a modern modular style coil but we replaced it with a similarly rated cannister style coil (also from Langdon). Could a power surge burn the module? Coincidentally, the radio also went out at the same time (its wired through the ignition).

steveg,

My first thought was improper coil, but as you note, the round coil you bought from Langdon has his blessing for this setup. Technically, the coil is on the secondary side of the ignition, so it probably wouldn't affect the module anyway.

I don't know if a voltage spike would take out the radio or the solid state module, plus I don't know if a generator is capable of producing such a thing. My first thought was that maybe the key was left on and something didn't like that.

From what I understand, these modules can and do fail. Maybe analyzing the type of failure to the radio would shed some light on the problem.

It could be coincidental. If the radio was fused, would the fuse pop on a voltage spike? I'm asking more questions then I am answering.

Stuart

You better check your charging voltage. Sounds like it might be too high & burning out solid state components. The wrong coil could cause a module failure. The original HEI dist requires a silicone grease under the module when it is installed. It transfers heat away from it. I don,t know about the aftermarket dist.

Is the engine grounded well to the frame & body? I have seen module burnout on non-grounded engines. Brian

...the engine is well grounded to the frame, the radio did burn a fuse when whatever happened, happened. We replaced the fuse and it popped again. The radio is a '42-46 accessory radio converted to solid state AM FM...I shipped it back to S&M Electro Tech in MN and they said it is running fine for them...they thought that maybe the battery cables were switched...they were'nt...or maybe the hot wire from the battery crossed/or shorted the ground in or around the ignition.
We've now replaced the module and rewired the ignition including a new ignition switch. Truck starts and runs fine again. I'm waiting to get the radio back from MN to see if that works out. But I would really like to understand the potential causes for this kind of malfunction. Thanks for all the help.

Sounds like most bases have been covered, give it a whirl & let us know how it goes. Brian

coil, internal or ex.......ballast, not familiar with 12 volt gen...........must go to alt during the conversion.........

I ran a 12 volt electronic mallory dist on mine, almost drove me nuts trying to find a small gremlin, like it would always start, idle good but got into a habit of dieing at hiway speeds and lower...always would restart.........the problem got really bad so I had to find out..........the module was bad, heating up breaking down..but yet the tests said it was ok.... I bought me a spare for future, it had been on the truck for about 8 yrs so those things happen... the book said to make sure the wires/clip from the dist to the engine were disconnected when ever it was jumped off... I never thought about doing so when I did need to boost.. that may have helped with doing something to the module......... anyway, glad you got it running.

I had a module in my HEI (from Tom Langdon as well) fail - never did figure out why.

steveg,
The previous posters were correct in that the modules go out occassionally and can test good even if they are bad. Another thought that I did not see covered was if you had replaced the wire from the ignition switch to the HEI so that it was not being run thru the original resistor since this reduces the voltage and can overheat the modules too. Just a thought.
Happy motoring!