I have a 2000 GMC Jimmy I bought a few days ago. I noticed that my headlights are on ALL the time no matter what position the knob is in, but they of course they go off when it is not running. AND the dimmer doesn't work either, but it is getting power to it because if you put the dimmer all the way up until it clicks the dome lights come on. Could the switch be bad? Could it just be a fuse? Please help. Thanks a lot!! 