Killing Ignition Control Modules

[72K10]

I've blown two ignition control modules in the last two months. Anyone have any ideas on why these modules blow? Lack of amps / volts, too much?

Chris

[old Rusty C10]

were they the same brand name fromt he same store? ive gone through two KEM modules for a cavilier one time and it was a bad batch at the auto parts store went to a delco for #3 and its been in ever since like three years now

[72K10]

First one was a Summit, second was a Napa. So I don't think it's poor quality modules.

[Piston]

Couple of things (but not all) will cause that. Voltage spikes from a bad pickup coil. Everything will work fine until the module has had enough ac spikes from the coil, eventually causing it to fail.
Another thing would be high primary resistance in the igntion coil.

Also check the battery voltage at your Dist' (while running).

[jhow66]

Check your coil ground in cap.(If HEI)

[Downtown]

Did you put the grease that came with modules on the back of it? That grease helps discipate the heat and keeps the module from overheating and burning up. Just a thought.

[72K10]

Yeah, I slabbed on the grease. I had been having some electrical problems prior - burned through a couple of alternators. Don't know if that might have contributed? Just want to fix the problem once and for all.

[Piston]

Make sure you have a stable charging system first. Voltage spikes or high voltage from the alternator can have the same affect. Usually though, you'll pop a few light bulbs before the module goes out (if its a stuck regulator or simular)

[Huck]

If you are burning out altinators, you have another problem that will continue to kill the modules. You probably have a dead short somewhere that is wiping out the diodes. Hate to say it but it's probably time to do a wire trace ----unwrapping and going through the front harness especially where it bends off the radiator support by the battery-(acid sometimes eats the insulation here)--and on the drivers side as well. There are two little fuses in this harness that need to be there as well. GEt a couple of rolls of tape and take your time unwrapping and rewrapping. Find the short and you will more then likely find the cause of the module blow out as well. Good luck--Huck

[72K10]

Huck and Piston, I already traced the short down and fixed it about 10 days ago. The charging system is working fine now. That's why I wonder if it isn't something else. If it were the spikes in the charging system, I thought the module would have failed near that time. Also, I've heard that modules blow all at once, but both times for me the pickup got hard to start (low juice, I guess) for a couple of days prior to completely going kaput. I wonder if that wasn't the module going south gradually?

[Piston]

If the charging system is ok now, focus on the primary side of the igntion system (pickup coil, module, coil, ground strap for coil) There is always that slim chance you got 2 bad ones in a row, but these items are easy to check using a DVOM (digital volt ohm meter) and will rule out any future problems.

[Huck]

Another possibility is the condenser. Had a 71 that ran fine except when it got hot or it rained, then it didn't want to start or run worth a darn. Turned out to be the condenser!! The modules tend to be good or bad, I agree, HOWEVER, I've had more then one that performed ok at low rpms but break up at higher rps or when hot. That being the case, I would suspect that the "yes/no" rule on modules is not absolute. The condenser is a cheap swapout that might me the problem and couldn't hurt! Huck

[72K10]

I checked the ground to the coil when I replaced the module (today). All seems to be good. Thanks, Piston. I don't have the expertise to check the resistance of the rest of the stuff. It also runs well now with the new module, so I'm thinking that the rest of the ignition system is good. Huck, I read in a service manual that the condensor for the HEI doesn't relate to the ignition system like the points distributor condensor; the manual said that it's there for radio interference. Doesn't seem to make a lot of sense. I appreciate you guys comments; if you don't hear from me, then the module is working out OK. Thanks!

[ChevLoRay]

My experience is they are working, or they are not. What I have seen is, "Well, it was running okay when I parked it here, but now it just won't start at all". Regardless of where you parked, when it quits, it quits right then. NAPA sells two grades of these modules, one has a one-year warranty, the other a lifetime warranty. When you compare them, the most difference you can see is the box they come in. I paid the upcharge and had to get the module replaced a year later....after only 2000 miles of use.

I would go ahead and replace the condenser, too. It comes with the lead attached, if I remember correctly. You have to be sure and use the dielectric grease (the white gooey stuff) when you install the module. If you thought it wasn't necessary, guess again. NAPA sells the stuff, but it ain't cheap and it didn't come in a tube....just a box with 10 little capsules of the dielectric grease for more dollars than I care to spend, again....just because I couldn't find the one that came with the module. Live, and learn.

[texnician01]

Make sure that you have a good ground from the engine to the frame. those ignition modules tend to burn out if you have a bad ground. It forces too much current through the module and destroys it. I work at Oreillys and see a lot of them come in and this is usually the problem. good luck.

Nathan