I realized recently that one of my KC Daylighter knock-offs is out. First, I tried replacing the bulb; still out. So I checked the input voltage and found that with BOTH fogs unplugged, the voltage coming off each lead was the same (12.75v). However, when I plugged in the working fog, the voltage at the other lead dropped to about 10v. Through trial and error, I discovered that when just one fog is plugged in, either one will work. But if both are plugged in, only the driver's side will light. I am using an ebay wiring harness with both fogs running off a 50a/14v relay. This only started happening recently, what is going on?

 

bad ground...

 

Not the ground. I cleaned it up and no change. However, I did find a fix. I just switched the two power leads between the fogs. Go figure; no idea why that worked. I hate not knowing.

EDIT: Nevermind, passenger side is out again. Shoot.