Highbeam Headlamps Inoperative

From Doug Dwyer

I think I would be more suspicious of the headlamp relay, but that's only my opinion. Recent and very good info on repairing the relay can be found at Near as I can tell, the only function of the column mounted high beam switch is to provide a ground for the control-side of the relay, thus "pulling-in" the contacts. So...... To narrow the problem down a bit, try this: Disconnect the blue/black wire from the relay. Arrange a 12 volt test light to check for ground and probe this wire. Now, exercise the dimmer switch back and forth....you should see the ground come and go. If it does, then I'd say the switch is doing it's job and your relay is stuck. If the ground stays constant when you operate the dimmer switch then I'd say you have a switch problem, as you've suggested. Easier to replace the relay than the dimmer switch, so, IMHO, this merits some double checking. And, with Mark's super explanation (link above) you can repair the relay.

From Darrin Hodges

I have just had the same problem, after checking the switch function as doug suggested earlier, i jumped in pulled the relay apart, only to find it ok. It turned out to be the brown wire that feeds +12v to the relay, it goes back underneath the headlight fusebox into a 3 way connector, which was gunked up, preventing sufficient current through to trip the relay. cleaning up the 3 way connector restored the relay function.