Tomctomc,
OK let me try this again; above I was referring to a normal load (such as head lights, tail lights and dash lights) all which go through the headlight switch bimetallic breaker. The breaker switch has points just like the points in a distributor. If the contact surface is dirty and corroded the current is reduced due to the resistance and heat is produced (just like a resistor or light bulb). Since the construction of the points is bimetallic, the points separate, causing all of the lights to go out. I am not talking about dirty contacts elsewhere in the circuit, which I agree with you; just the breaker itself.
I understand the breaker is designed to heat up only when there is too much current through the points, which also causes it to heat up and open, but correct function requires a good contact between the point surfaces. I experienced this phenomenon one time and was burned by the hot breaker when I reached under the dash in an attempt to find out why I suddenly lost lights. My switch was aftermarket which had a replaceable breaker which allowed me to fix the problem by replacing only that element of the switch.
Kent
