I recently did the fog light mod (bypass switch). I believe most of you are familiar with it. It works great with one exception. There were 3 wires running into the side marker light. I tested all 3 with the switch in the parking light position. Only one wire was hot. I spliced it, taped into it and ran a wire from there to the relay. Everything worked cool. I turn on the running lights and the fogs come on with them. That night when I turned on the headlights I realized that the fog lights cut out. The running lights stayed on. I don't understand the connection? Doe's the power source switch to the another wire when you turn on the headlights? What's going on?

 

did u make sure to bend the pins that go into the socket which engage the relay with the headlights,maybe they caused a short