Tiger03447

Dear Listers and lurkers: As some of you who have been here on R-list for a while, you know that I have been groaning off and on about the fog light circuit relay sticking and causing a fire under my dash. Well, I found a replacement harness recently, but there were a few down sides to it , but it was better than what I had. It was not set up for A/C nor was it rigged for two cooling fans. So, recently I pulled out the entire harness that controls the lights, fan(s) headlight motor and the thermostatic switch that controls the fans. So, today, in an effort to see how the old harness ran the two fans, I cut it open, and I got a REAL surprise. When the harness under the dash burned, it also fried the entire harness all the way down to the fog lights proper! So word to the wise: fuse the fog light circuit as it is unfused and change out your old double relay. The fog light fuse in the fuse panel does NOT do the trick for protecting your wiring harness. Comments and suggestions are welcome. This is for EARLY cars only, AFAIK. Thanks for the rant.😀

orig944

Are both the left and right side wires burned, or only one of them?

Tiger03447

Both…from the relay all the way down. After talking with a guy much more knowledgeable than I, we determined a pair of 8 amp fuses between the double relay and the lights , would be good protection for the downstream harness. The fuse block fuse is between the relay and the battery, ie.. on the wrong side of the harness. Presumably this was corrected in the 85.5 cars and later models. The wire gauge on these wires is too light for the job IMHO. The bulbs pull 55 watts each. I changed mine to LEDs for a lighter amperage draw and more light. Once the relay sticks your total wiring harness is trashed along with a lot of other wires not in the harness. Guess who is putting in line fuses into the new wiring? 😀

orig944

This is an important clue to what actually happened to your car. The light bulbs themselves do not generate current, and it is unlikely that both circuits which originate at the fuse panel shorted out, causing a current load that scorched the wiring on both left and right circuits. What I believe, based on this information, is that a previous owner installed higher wattage light bulbs in the fog lights. They are supposed to be 55W, but 100W bulbs are available, and perhaps even more. The increased current of the higher wattage bulbs would overheat the wiring of both circuits, causing the damage you see. The increased current could also overheat the relay that caught fire in your car and extensively damaged your wiring harness.

Obviously this is only a theory. But in order to scorch the wires going from the fuse panel to the bulbs, and indeed both bulbs, there needs to be an explanation why there was excessive current in both them. The bulb itself should limit the current to what is acceptable for the harness, and apparently this limit was exceeded.

Tiger03447

The fog lights had LEDs in them which, IMHO, lightened the wiring load on the harness. So, I’m still going with the bad relay, which I’ve looked at . It seemed normal in appearance and was not burned up. I would’ve thought, that it would have been burned up totally and the cover melted. No so. Basically, now it’s just a fix it scenario. I intend to put in some fuses between the relay and the fog lights. Perhaps this will save my new harness from more destruction.😀