What headlights are in the car? If you have a set of halogens in there the high beams might be drawing more current than the factory wiring/switch want to deal with.
And all of the normal check the grounds, check the switches, check for loose connections stuff applies too. But the headlight wiring and switch on these cars can't handle a ton of current, and a newer set of halogens could do them in.
@crackedback makes a really nice headlight relay wiring set up that solves the factory wiring issues with the headlights.
