'87 V-12 Extremely hot Lucas ignition module
 

I started my '87 from cold today, and after a few minutes touched the Lucas ignition module. It was extremely hot, too hot to touch for very long. The intake manifold at that point was much cooler. I also have an '85, so I started it also. Its ignition module gets warm, but not hot. What could be making the module in the '87 run so hot?

Jon

You can open up the box and replace the internals with AC Delco. It's basically a GM HEI module inside

I'm planning to do that. I'm wondering if one or both of the coils are going out. I'll check resistance tomorrow.

Jon

I'm not so sure that the cooler module on the '85 car isn't the abnormal one.

The HEI module creates heat. The Vaseline-appearing heat sink compound that you smear under the module is supposed to help carry heat out of the module and into the amplifier case . I wonder if the compound wasn't used the last time the module was replaced...or has perhaps dried up after 30 years if original?

Just a thought.

Cheers
DD

In my experience HEI modules last about 5 miles with no heat sink grease, companies sometimes supply the improper "dielectric" clearish grease as opposed to the proper "white" heat transfer grease. You can pick up the correct stuff at any Radio Shack or computer store.

However hot it gets, if it is working OK, leave it. Mine runs hot and always has. The Great Palm has something about this, apparently the slower you go the hotter the unit gets as it creates and has to dissipate more heat at low revs for some reason.
Greg

I have a newone on mine and it gets hot to touch, thats just how it is

Yep, some bake, some dont.

Mine is out the front near where the 2nd coil once was, and at idle, oh boy, but after a run, the rest of the engine is obviously HOT, but if you reach in, it is coolish, but with the engine idling gets quite hot quite quickly.

Inner module brand has made virtually no difference.

I would, just for giggles, check the engine straps, and make 100%, or more, sure they are doing the right thing. Most are not, and electrickery does not like a bad earth.

So, if things are right, the module develops heat in operation.
The right goop facilitates heat transfer to the case. And from the case to the air and to the engine???


My LT1 uses a similar module and coil. heats ink and goop, but mounted to the front of the left head. Air and coolant for heat transfer.


A rule in electrickery is resistance becomes heat. Tolerated when needed not always needed.


One of my house fans quit. I might have another go at it. simplify it's complex electrics.


The one that I fixed by eliminating it's articulation and adjustment, making it fixed works so nice. Wood in lieu of plastic. First design a bit lacking, but functions. I could do the more elaborate version, but function would remain the same, so...




Carl

Thanks guys. For good measure, I'm going to check my coils, cap and rotor, and change the module with some fresh heat sink compound. Electronics getting so hot it burns, really bothers me. I've had a bit of rough running over 4000 rpm also, so it's time to check. It's only got 50k miles, and things look pristine, but looks can be deceiving.

High resistance coil is a 1st stop for revs issues.

Also spark plug gap too wide, usually an idle issue, but not always.