Headlights do not turn on

The switch is the logical suspect, but you also have to inspect the connector terminals. Most head light switches incorporate a built-in auto-resetting thermal circuit breaker. Those cause more problems than they prevent. The contacts develop a little resistance which causes heat to build up. That leads to more resistance, and more heat, until the circuit breaker trips intermittently or fails to make a good contact.

This same thing can happen to the switch contacts, but typically that starts out where you will see the lights turn on when setting the switch just right. Either way, that heat migrates out to the connector terminals, and two of them overheat. Those must be cut out of the connector and be replaced individually, otherwise they will also develop heat that damages the contacts in the new switch. I can describe that in more detail if it becomes necessary.

First look at the terminals on the old switch. Most commonly you will find two that are dark, or the housing around them is charred. There will be two matching terminals in the connector that are also dark, and the plastic around them will be melted. Those are the two terminals that must be cut out of that plastic. Remember which wire went to which terminal.

Plug the connector into the switch with those two terminals missing. Now, you'll notice on those two loose wires, they are really hard for the first four inches. That was caused by the copper becoming hot. Solder will not adhere to that, so cut that four inches off. Splice on a new 4"-piece of wire of the same diameter. The best way to do that is to slide the strands into each other, press down any sharp points that are sticking up, then solder the joint. Seal it with heat-shrink tubing. Never use electrical tape in a car or truck as it will unravel into a gooey mess on a hot day.

Crimp on a universal terminal onto the end of the wire, but also solder it for a solid connection. Squeeze it a little tighter so it holds on really well and makes a good electrical connection, then plug that wire in separately through the area you cut away in the connector body. Do the same repair for the second wire.