Ignition module leak?

Further to Vinny's hint, there's not much on the underside of the modules that should conduct heat very well.  That potting compound won't conduct much heat, and it doesn't have any fins to have a lot of surface area for heat transfer.

I think the best thing that can be done for the module is to extend the wires and put it on the fender itself like Ford did in the late 70's.  Use the fender as the heat sink, with outside air flowing over the fender to cool it.  And, you are then getting the module away from the exhaust heat.

It is interesting that the Ford Motorcraft ignition modules that were used in the late 1970s had cooling fins built into the aluminum casing and were mounted to the metal fender.

When the Bullnose trucks were introduced for the 1980s, the ignition module was changed to a completely smooth aluminum casing (no cooling fins), and they were mounted to the plastic inner fender.


I have had an aftermarket ignition module, a new Motorcraft ignition module bought from the dealer about 10 years ago, and a NOS style Motorcraft ignition module that was originally used when these trucks were new.  Both the aftermarket and the newer Motorcraft ignition modules looked about the same. The NOS Motorcraft ignition module is taller and quite a bit HEAVIER than the other two, and the potting is a bit different.  Most importantly, this module feels cool to the touch when the other modules felt warm to the touch under similar conditions. Lucille *seems* to start up quicker and run cleaner with this one, so this is the one I am using.  

Plus, it has a cool "DURASPARK Ignition - Tested Tough" sticker on it with lightning bolts!  

LARIAT 85 wrote

Plus, it has a cool "DURASPARK Ignition - Tested Tough" sticker on it with lightning bolts!  

Like this?

https://www.ebay.com/itm/NOS-FORD-DURASPARK-IGNITION-CONTROL-MODULE-NIB/232993063752?epid=1925474158&hash=item363f780348:g:dz8AAOSw8m5btDRX:rk:1:pf:0

I agree - too goofy.

If you were to put a second, spare, module above the other in the fashion I did you'd have a bit of additional cooling.  But, the small 1/4" nuts won't have a whole lot of thermal conductivity due to the small surface area/foot print.  So anything you could do to create more contact would be of benefit.  Washers with thermal grease where they contact the two modules would help.

Stacked washers acting as the spacers would work, but you could up the ante significantly if you'd alternate large and small washers between the modules.  The air could flow 'tween the big washers and that would act as a radiator of sorts.

I am not sure what all the fuss is about?

A Ford Motorcraft ignition module that leaks out its potting or fails from heat is the exception, not the rule. There are many vehicles out there on the road with the original module still in place without washers, spacers, etc.  Yes, a spare is good to keep on hand, but you know how that goes - whatever you have a spare of will usually *not* be needed.  

I don't see it as a fuss, but just thinking of easy ways to prolong the life of a DS-II module.  The fact that several of us have had them fail or the potting run out suggests that it might be prudent to provide some insurance against having that happen again.

I wonder if Ford made a mistake when they moved the module from the metal fender in '79 to the plastic inner-fender nearer the engine and exhaust in '80.  That both upped the temp the module would see and, at the same time, dramatically reduced its heat sink.

Further, might the same team that made that decision be the one that thought mounting the TFI module on the distributor was a good idea?  It wasn't, and they had to move it to the fender - right back where the DS-II module was in '79.  In other words, full circle.

Good point on the TFI ignition module.  I didn't think about that.  Mounting it on the distributor was a bad idea for sure.  Like you said, it is interesting that Ford went full circle and later moved it to the metal fender.

That being said, I put a nut between the ignition module and fender apron to lift my ignition module up a little to provide some airflow underneath.  I remember reading a post at FTE where someone said (I think it might have been NumberDumy) that Ford issued a TSB to raise the module up off the fender for better cooling.