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Old 06-02-2002, 07:57 AM   #1
MJN
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HEI control module

I have been having trouble keeping control modules in my '72 Blazer. We just put in a brand new distributor about 7 or 8 months ago and I had to put a new module in before school. We went through two of them with the old distributor also. What could be going on? Too much heat or vibration? It seems like they slowly get weaker and weaker then it doesn't start one day. Anyone else have this problem? The next time it does this I'm going back to points!
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Old 06-02-2002, 08:06 AM   #2
bobs409
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I know what you mean, im not into "electronic" much myself. 5 of 6 of my vehicles have points. LOL Make sure you carry a spare module and tools to replace because as you probably know, when they go, they're gone.

2 things that come to mind that may cause problems are;

Did you put the special grease on the metal side of the module that helps disipate heat? If not, heat may be doing it.

I would also check the voltage going to the coil. Check to be sure your not overcharging.
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63 Impala 283/PG/3.36 (under restoration)
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Old 06-02-2002, 10:08 AM   #3
71GMC_3/4T
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You might want to try one from Chevy garage, or a high dollar one from Napa.
There must be a reason the ones from checker and autozone are dirt cheap...
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Old 06-02-2002, 10:24 AM   #4
MikeB
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Spend the bucks and get an P/N 8364 HEI module from MSD. It will output more current to your coil and will last forever. At a later date you can also get their HEI coil. http://www.msdignition.com/

Cost is around $68 at Summit Racing.
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1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes.
1982 C10 SWB -- sold
1981 C10 Silverado LWB -- sold, but wish I still had it!
1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming.
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Old 06-02-2002, 11:22 AM   #5
Zkast
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There are a few things that will "knock" a module out.

Voltage - If your running over 17v for extended periods of time it will overheat and burn.

Pick-up coil - If the coil is bad it will send ac voltage spikes to the module and kill it. The module is normaly switched with a ac signal from the coil but after age/time the coil will start to send irratic signals acting more like a capacitor.

Bad ignition Coil - If the primary windings in the coil have to high of a resistance it requires to high of a load in the module which will burn the module out after time.

The easiest thing to check is the coil (most probable). If you need a schematic and values let me know and I'll post them. Most cheap manuals show how to test for a bad coil though.

Oh and the most important thing... Buy good quality modules. Standard, Borg-warner, AC Delco or MSD have good aftermarket modules. If your using WELLS ignition parts you can start by replaceing that first LOL.

Good luck with it.
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