Every winter my heater relay fails at least twice. The terminal on the relay that connects to the orange wire (power to the blower motor) gets so hot that it melts the plastic substrate around it and the blower motor quits. I've learned to keep an extra in the glove box because this is very inconvenient in Alaska during winter. This happened twice this morning within a span of 10 minutes. At $30 a pop, I'm economically opposed to replacing another one until I know what's causing the relays to melt.

I searched the forums and found many instances where the relay goes bad, but I haven't found anything concerning WHY they melt.
Any help here would be appreciated. It's about -15F right now and I'll have to drive home with my windows down so they don't frost over.

Thanks,

Jon

 

Your wire terminal has probably oxidized and the heat from the resistance to the current is melting things. Fix the crimp connection by removing the crimp, peeling back the wire to good clean wire, clean up the grimp connector, re-crimp, and solder.

 

The crimps don't show any oxidation. They're all still pretty shiny. The tiny bit of exposed wire looks good too.

The first relay that failed this morning has worked fine for the last 8 months. When it went bad this morning, there wasn't much melted plastic on the relay. The replacement I installed quit about 5 minutes later and was severely melted around the hot terminal.

 

Brrrr..... makes me shiver just thinking about -15. I had a 76 F-100 that had similar problems. Traced the source of the problem to be two fold. Found that the contacts ( rivets) running through the plastic substrate of the fan relay were not making contact. That is, the "rivet" crimping the external connector to the internal wiring was loose, allowing oxidation to insulate the external wiring from the internal wiring of the relay. I used a center punch to restake this "rivet" and cleared up problem #1. #2 was a bit simpler. There was light surface rust on the underside on the dash where the relay mounted. Cleaned the rust and made certain there was a good electrical contact for the relay mount. I know that it would seem strange to have the same problems with multiple relays but I have seen stranger things. If the factory has a manufacturing problem (like insufficient crimping pressure for mounting rivets) a large quanity of product could be on the market before the problem is realized and addressed.
If you haven't all ready, be sure to check the condition of your fan motor as well as making sure you have the right size fuse protecting the fan motor. A high current condition could cause the relay to smoke, though the fuse should open first. Hope this information is helpful. Good luck.
Roger Carter

 

Try soldering that wire anyway b4 you have more problems.