Please help me trace this problem to it's source.

I installed 4x6 KC lights, KC 20A relay. The parking lights are the trigger, the switch I added to the dash controls the lights. Everything works fine, but the relay buzzes. I swapped the relay, same problem.

How do I determine what's wrong?

 

A bad ground is often the cause of relay buzzing.

 

If you want to try something, take the relay trigger wire off and move it to a hot wire and see if it still buzzes.