I've been having the same issue. I have a pair of KC HiLites Slimlites that I hooked up last week, with no luck. My switch comes on just fine, so I know power is running through the relay, but the lights won't come on at all. I've called KC twice, and I've been told to replace the fuses (which aren't blown but I did anyway), and to reground the relay (which I've done as well), both to no avail. Here I am a week later, with some lights that look really good on the Jeep, but are completely functionless.