Headlights will not turn on?

First check Fuse "G" under the hood. That is a large 50-amp maxi-fuse.

The most common failure is the head light switch, but there is usually more involved than just plugging in a new one. The second best suspect is the dimmer switch.

The head light switch has a built-in auto-resetting thermal circuit breaker. Those cause more problems than they prevent due to the contacts becoming arced and pitted, then the less-than-perfect contact generates heat which causes the circuit breaker to trip. The clue though is the head lights almost always flicker on and off every few seconds.

First check if the tail lights and the dash lights work. If the tail lights do not work, the head light switch is the better suspect because the dimmer switch is not involved in the tail lamp circuit or with the dash lights. If the tail lights and dash lights do work, it is not conclusive of either switch being good or bad. For that, the easiest is to pull out the head light switch to inspect it. Unplug the connector from it, then examine the terminals on the switch and the plastic body of the connector. Very commonly you will find two of the terminals are black, and the plastic body around them is melted. These melted wires will be red/white and light green.

If these terminals look clean and shiny silver, you may need to go to the multi-function switch and check the terminals there too, but remember, if the burned terminals are there, the tail lights and dash lights will still work.

Before you dig into the multi-function switch, go back to the head light switch, and with it plugged in and turned on, measure the voltage on the red/white wire by back-probing next to the wire. You should see full battery voltage of 12.6 volts there all the time. If you have that, measure on the light green wire. You should find the same voltage there only when the switch is turned on to the head light position. If it is missing there, the switch is defective and must be replaced. While it is much less common, you can have a bad switch with no overheated terminals in the connector.

If you do find two black overheated terminals, you must replace the switch and those two terminals. If you don't replace the terminals, they are guaranteed to make a very poor connection, and the resulting heat will migrate into the switch and start to deteriorate its internal contacts too. You will have the same problem very soon. To replace two black terminals, cut away the plastic part of the connector body that is melted, and cut off the two terminals. Plug the connector into the new switch that way.

The two old wires will be stiff for the first four inches from being hot. Solder will not adhere to that, so cut that four inches off. Splice on a four or five-inch piece of wire the same gauge by sliding the strands into each other. I do not like to twist them the way we do house wiring because that makes it too hard to seal the splice. Press down any sharp ends of wire strands that might be sticking up. Solder the splice, then check again for any sharp points sticking up. All you have to do is press them down with a small pliers so they do not poke through the heat-shrink tubing.

Slide on a piece of heat-shrink tubing, and heat it to seal the splice. Never use electrical tape in a car. It will unravel into a gooey mess on a hot day. You can buy heat-shrink tubing with hot-melt glue inside to seal out moisture, but that really is not needed for this job. Splice on a piece of wire to the second wire the same way. Now, crimp on a pair of universal crimp-type terminals, but also solder them to insure a solid connection. Squeeze them just a little to tighten them where they slide onto the terminal on the switch to make sure they have a good connection, then plug them into the switch individually through where you cut away the melted connector body.

If you should find the burned terminals are at the multi-function switch, do the repair the same way to those wires. This problem always has a chance of occurring again, so when I do the repair, I splice in about a nine or ten-inch piece of wire. That way if I have to cut off four inches next time, there will not be any need to splice on another piece of wire. Just cut off the hardened part and solder on a new terminal.

If you do not find any overheated terminals, do the two voltage tests. If you have 12 volts on the light green wire, we will need to go to the multi-function switch next.