If you have a short via the wiring on the high beam side, the internal circuit breaker will open. The question is if you gave it enough time in that condition to see if the lights come back on and then off again without touching anything. That would show the breaker trying to work. Once the arm cools down, it should make contact again.

I clean lots of corrosion build up between the two breaker contacts all the time. You can test the breaker only without taking the switch apart. Disconnect the switch connector from the switch. You can check the breaker separately by using an ohm meter and connect one lead to the top vertical terminal on the headlight switch. Touch the other lead to the small tab that is rolled over to the right of the bottom horizontal terminal. That will test to see if there is resistance (corrosion) going across the breaker. That should read 0 ohms.

Then connect the second lead to the bottom horizontal terminal and read that impedance with the switch in the headlight on position and that too should read 0 ohms.

While you are testing the switch, take a look at the two inner terminals to see what sort of reading you are seeing. Once again, your meter should read 0 ohms. The parking lights are fused and do not run through the internal relay.

Anything less than 0 ohms and shows a negative reading is reducing the light output of either the headlights and or parking lights.

Jim