eyeteeth wrote:
Well then... mine would be the third. Mine is in better condition than TreeSeekers, components are still covered. But it still melted out.
I must be very, very lucky.
It's my impression ICMs get their negative/ground connection through the wires. I could be wrong. I may go out, pull the ICM from the parts donor Dakota, and look at the printed circuit board (PCB) inside. Specifically, I'll look at how PCB is mounted to see if any of the PCB's 'traces' lead to the metal case.
I may have fallen prey to a common cause of misunderstanding. Motor vehicle wiring diagram almost always just show the positive side of the circuit, without so much as a single ground symbol.
I do know heat is a
big issue with ICMs, due to seeing it pop up repeatedly in things I've read. VintageMopar is correct, that big transistor generates most of the heat. Especially when it's cycling/switching 25-50 times per second. That's why it's mounted on the ICM's surface.
Paint is both an electrical and thermal insulator. So, I'd avoid any ICMs that are painted.
ICMs that don't specifically have heat sinks
may be okay for normal operation. Less than ideal circumstances would make them iffy.
Aluminum is a reasonably good heat conductor. Copper is much better, approaching ideal, but more expensive. This is why most heat sinks are aluminum. Of the three metals, steel (which is mostly iron) is least effective, tending to hold heat rather than dissipate it.
(Think copper versus aluminum versus steel and cast iron cookware. Less expensive pots and pans tend to be aluminum. Advertisers stress copper in their coolware because it conducts heat better. Cast iron skillets and dutch ovens work because they hold heat.)
Surface area is important in terms of dissipating. So, finned heat sinks are more effective, with the more fins the better.
So, the ICM TreeSeeker found, specifically mentioning copper heat sinks, leads me to believe it is comparatively good. 'Weld' is probably a misnomer ... copper is almost impossible to weld because of how well it conducts heat. (That's why alloys with high copper content tend to be brazed or soldered.) Regardless, welded/brazed/soldered heat sinks are better able to draw heat away from components ... so, another indication of quality.
('Laser' tends to be an advertising buzzword. However, laser etching, versus tradition photo-chemical etching, leads to better quality assurance in mass produced printed circuit boards.)
Assuming I was mistaken and ICMs do need/use a chassis ground, loose/faulty mounting would add to the heat problem through unacceptable electrical resistance to ground. (Electrical resistance equals heat.) In this case, I'd be inclined to add a dedicated ground wire rather than rely on common chassis ground.
