Headlight Issue

I have an 88 TC and it has a few odd problems. One that really bugs me is the phantom headlights. On low beam they work fine 99% of the time. On high beam, after about 10 minutes with them on, the lights blink off/on then off and stay off until I switch to low beam. Last night the low beams wouldn't come back on until I turned the lights off then back on again. I spoke to the guy I bought the car from and he says maybe the dimmer switch? He had a similar problem with the twin to my car and eventually the headlights quit all together. He fixed it by bypassing it to a switch before another problem sent the car to its leafy grave. The dash lights and all the rest stay on without a hitch. Are there any relays I should check? I looked around here in the forum and found a similar problem but I don't have the auto-dimmer feature so that solution didn't apply. It's getting time for inspection and I need this problem fixed. Any suggestions will be greatly appreciated!! Thanks guys!