I'm on my 4th ignition module in my '73 with DFI and Comp Controlled ignition. I am wondering at this point if maybe the module's ground has got some resistance in the return circuit. The parts guy told me the module grounds through the back where the metal heat sink is, and returns through the distributor body.

Does anyone concure with this? I might add a separate ground wire back to the negative battery terminal from the bottom of the dist if that is the case.

thanks
dr


[Modified by DavidR, 9:32 AM 1/24/2003]

 

Forgive me, but I have to ask... are you putting a nice thin layer of grease on the metal plate of the module to dissipate the heat?

 

Tried thick, tried thin. Still burns up in about a week of driving. It leaves me on the side of the road. Motor usually just dies while I'm driving - poof - no more module. Pull the cap and it has a brown burnt spot right near the 2 prong connector. Pop in a new one and away we go.

thanks
dr

 

How many pins does your module have? The ones in the C4s are 7-pin units. If you have a 7-pin also I can look up my wiring diagram at home.

 

The module is a little different from those on a C4. Mine matches a '92 camaro module. Those distributors have remote mount coils.
There is a 2 pin and a 4 (or 5) pin connector on the outboard side of the module. The burnt spot is always near the two pin terminal, on all three that have burned up.
Maybe the Accel ECM has a problem and is burning them up?
thanks
dr

 

ttt :confused:

 

By any chance is there a resistor in the +12 volt line to your distributor??

If not, measure the RESISTANCE of the connection from the +12 volt source to the connector supplying the +12 volts to the distributor.

DO NOT just disconnect the + 12 volt feed and check for +12 volts there.
(It WILL be +12 with no current path)

You MUST know there is NO resistance in the +12 volt feed line.

My 73 truck had a regular looking wire going to the + side of the coil.
Guess what??? Ir was a RESISTANCE wire and IF I had used that to supply the 12 volts to my HEI conversion I'd have burned up modules just as fast as you are doing.
It was a pizzer to find because I kept looking for a resistor.

Your mechanics are close to the right issue... just on the wrong side of the distributor.

Technical explanation::
The ignition module switchs from +12 to 0 or ground.
When it's not conducting theres no power dissipation in it.
When it switchs on to 100% conduction the power dissipation is minimal.
At 50% it will get hotter than a MF'er.
It needs the complete 12 volts to make the transition to 100% conduction.

ANY resistance in the feed wire will cause this problem.
I'm betting your positive ignition lead is a resistance wire like mine was.

Use a fairly accurate ohm meter to check for this... you're looking for about 4 ohms. If you find that, then it's the trouble and causing the modules to self destruct.

Let us all know what you find.

 

What spark coil are you using? Is it the same one the spark module was designed to work with? If not, the "on" current could be so high that it exceeds the modules rating and causes a premature failure.