I think I know why some people's ICM are overheating, leaking, and malfunctioning.
The clue is in the picture of the
Hirev 7500 instructions Eric posted and the link to the
Jegs .pdf instructions I posted.
BTW - I believe the resistance (ohms) in both of these may be in error. Most of the stuff I've found on the web states 5 ohms for Dodge OEM single (two connector) ballast resistors. Likewise, 5 ohms for one side and 1.2 ohms for the other side of dual (four connector) ballast resistors. (Finding one of the ones I have and actually measuring is on my to-do list ... but it's dark outside and the weather is miserable right now.)
Both of these specify 7 to 9 volts at the coil's positive terminal when the ignition switch is in the run position. (Eric used a red box to outline the relevant section in his post.)
The voltage for a fully charged automotive battery is 12.7 volts. This is roughly 40-80 percent higher than what an ICM should be receiving during normal operation.
(13.5 volts is the approximate voltage in an electrical system with the engine running and the alternator working.)
Electronics, like what's in our stock ICMs, can withstand
brief periods of higher voltage. (Definitely less than a minute, preferably less than 15 seconds, and ideally 5 seconds or less.) Longer periods of higher voltage
will cause the device to overheat and can cause permanent damage.
The ballast resistor is intended to reduce 12-14 volts input to 7-9 volts output to the coil during normal operation. (i.e., ignition switch in the RUN position.)
Overheating due to extended exposure to higher voltage is the most likely reason some ICMs are leaking.
Possible causes of extended high voltage is:
1. A missing, bypassed, or faulty ballast resistor.
2. Incorrectly wired ignition system.
3. Cranking the engine for extended periods.(I can imagine everybody's reaction when they got to the third possible cause.)
This is an excellent reason why you should not crank the engine for more than 10-15 seconds at a time. Likewise, you should wait a few minutes between starting attempts, to give the ICM a chance to dissipate heat.
As I've stated repeatedly, Mopar ignition systems with single (two connector) ballast resistors bypass the ballast resistor when the ignition switch is in the START position, sending a full 12-14 volts to the coil.
On dual (four connector) ballast resistors, the larger resistance (5 ohms??) side is connected to the ignition switch's RUN terminal and the lower resistance (1.2 ohms??) side is connected to the switch's START terminal. The output on the RUN side should be 7-9 volts and the output on the START side should be less than but close to 12-14 volts.
(Depending upon your ignition switch, the RUN terminal may be labelled IGN or simply I. Likewise, the START terminal is probably labelled ST or simply S.)
On dual ballast resistors, it's entirely possible to get the connectors mixed up. Assuming it doesn't prevent the engine from running, crossing wires would cause hard starting, with the coil receiving less voltage than necessary for a cold engine. More importantly, the coil would be receiving more voltage than it should when the ignition switch is in the RUN position.
(I've seen a few pictures of connectors that
should prevent incorrect connection. However, a lot more just show a collection of individual connectors, leaving it up to you to know which goes where.)
There's more I could say but I'll leave it there for now.
Before closing, I will say I haven't, until now, really studied Dodge ignition systems. I haven't experienced any problems, other than one failed ballast resistor, and definitely none of the problems some people are having.
