hi folks, i have gone through 3 electronic control modules in 3 years. stock 307 malibu with HEI distributor. approx 5k total miles driven in that time. i pretty much know it should be a bit more reliable than that. bad ground? bad base and/or total timing? no tach is attached to distributor. the distributor lead wire is hooked straight to the ignition switch with fusible link. i am thinking the ground is supplied by the Distr. gear connected to camshaft. any advise? htx
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Two things I'd check.

Full +12V at all times to BATT post on distributor when key is ON or START (minimum 12ga wire supply)

Heat sink compound on underside of module when you replace it.

Where are you buying your modules. Don't buy the cheapest you can find.
As Dave said, make sure the grease is spread evenly across the whole bottom of the module for heat transfer.

As suggested on this site. I bought the NAPA brand for my HEI and so far it has lasted much longer than the other brands I was buying.

Change the coil.

Regards,

Milton

make sure your engine to chassis/body grounds are in place, usually there are three of them. Braided flat with ring terminals on each end.

ok cool, good feedback, will check all, thx

Often times the "thermal grease" supplied with aftermarket ignition modules is NOT the right chemical. It's usually clear dielectric tune up grease that is supplied, and it does not conduct heat well.
Get a tube of actual Heat Sink Paste, available from Radio Shack and other electronics sources. This is the correct compound, and is what was used OEM and supplied with better aftermarket parts. Clean off all of the old residue from the distributor and apply a thin, even coat to the bottom of the module.

Also, stay away from the modules sold in the chain parts stores (Auto Zone, Advance, etc.) The quality is dismal, especially the Wells brand from AZ.

As someone else mentioned, a slightly shorted coil can overheat the ignition module. It will still "work" but will severely reduce the life of the module. A new coil is cheap insurance.

Change the coil, they are epoxy filled, and DO NOT leach heat out of their windings. Therefore, they get HOT, which causes resistance, and resistance is current draw increase. Once the coil gets hot, the layering between all the windings can disintegrate, causing what my ignition system builder calls "layer shorting', which changes the loading on the coil, to the point it overworks the modules. Change the coil, make sure all the grounds are clean and in place, and, the sequence for the assembly is - carbon button is, cap - button with spring UP - insulator - ground bar in place - coil. HEI coils MUST be grounded. Path is coil to solid bar under it which is also the center bar in the 3 pin connector, small wire with round ring terminal to coil yoke, center wire in the 3 pin connector to the distributor body, to the screw that holds the radio suppression condenser/wiring harness in the body.

Anything that compromises the electrical integrity of the system, from connectors on the ends of the modules, to grounding, dirty connections, loose connections, is increased resistance, and increased resistance means more heat, and more current required, with module failure the most prevalent issue. Keep all the electrical connections and ground paths clean and tight.

The "grease" between the body snd module IS NOT di-electric grease, but a thermal heat transfer "paste". Electronics stores have this, same stuff used in computers between chips and mother boards. Di-electric grease is NOT the same stuff, it is for elecrtronic insulation to corrosion, as in the cap terminals for the spark plug wires to the rotor tip, NOT heat transfer.

Wells ignition products, available from many outlets, including CarQuest ain their 'blue line', and from Auto Zone, are top notch parts, and the Wells parts are also OEM GM parts for most ignition and electronic applications. Their HEI modules carry a lifetime warrantee.

I learned a lot hanging around a person that does ignition systems, and, NO, DEAN, I am not Dave.

Regards,

Milton

Wells ignition products, available from many outlets, including CarQuest ain their 'blue line', and from Auto Zone, are top notch parts, and the Wells parts are also OEM GM parts for most ignition and electronic applications. Their HEI modules carry a lifetime warrantee.

I was with you 1000% up to this point Milton.
It's been my experience, also shared widely by many others in the business, that Wells electronic and electrical products are among the worst on the market for longevity and quality control.
I will concede that I haven't used a Wells product for quite some time and the quality may have improved. It's also possible that the Wells products made under different names are manufactured to different specs. Caveat Emptor.

I agree totally with everything else that you wrote. Excellent info. :beers:

Personally I have better luck going to a self service wrecking yard to find a used GM module, it will have GM cast in to the plastic.

I've used the Wells line for over 20 years, no problems.

Regards,

Milton