A relay control module in a DURANGO failed? That is the ONE thing that didn't fail in my Durango the company gave me to drive for abotu four years. It had several problems between 96,000 and 155,000 miles, but that wasn't one of them.

On another note: Again, I repair electronics for a living, have for 28 years. I would LOVE to get my hands on a known-bad relay module and see what I find.

See... back years ago, we had Scanner modules in Motorola Micor police radios that failed often - it was an odd manufacturing defect that was VERY repairable. It took about 20 minutes to fix with a soldering iron, sharp knife and some solder. The fix was forever - the factory had made a critical but simple error in manufacturing that took abotu 2-5 years to show up. You desoldered, scraped the islands clean around a certain transistor(s) and then resoldered. The board would NEVER fail again, if you did it right.

This failure of "solder cracking" sounds like the same thing. It CANNOT get hot enough under the hood to melt solder - rosin core solder melts around 500F.

I would lay money on this bet: This is not a heat problem, its a manufacturing technique problem of some sort. Heat only plays a secondary role here, heat causes things to change size and "make contact" at the right temperature. But the PROBLEM is in the soldering/assembly of the board. Soldered connections are reliable - when done right. When done wrong, they are the source of TERRIBLE intermittant failures that can be AWFUL to find!

Sure would like to see a "failed" board and see what's going on.