Hi Bruce. Welcome to the forum. Not the headlight switch but the dimmer switch which is built into the multifunction (signal) switch. First remove the trim covers and check the electrical connector for signs of melting or overheated / burned / blackened terminals. The overheating can occur from resistance in the connections between the terminals and switch or between the internal switch contacts.
If the connector looks ok, grab a test light and look for a wire that has 12 volts when the headlight switch is turned on, a second one that turns on when the headlight switch is on AND the multifunction switch is on low beam, and a third wire that has 12 volts when switched to high beam. If you find all three of those wires, the switch is ok and we have to look further for a wiring problem. If you don't find a wire that becomes hot with the high beams on, suspect a defective dimmer switch, but to verify which wire you should be checking, I'll have to visit the Ford web site to get you that information.
Also, a lot of vehicles now involve a very unreliable computer to the headlight circuit. You may have a Front Electronic Module (FEM). Beats me why they went to this insanity as this adds a whole lot of complication and huge repair expense. In the meantime, also look for a high beam headlight relay under the hood. If there is one, switch it with a different identical one to see if the high beams work. That's a quick way to tell if the relay is defective.
Sunday, October 10th, 2010 AT 5:22 PM