Over time, the headlight switch on a car can become worn and eventually inoperable. These switches can often be quite expensive to replace. An inexpensive solution is to wire a simple toggle switch in place of the headlight switch, which generally also controls the driving lights. Toggle switches are available at most auto parts stores as well as electronics retailers, such as Radio Shack, and can usually be wired up without too much trouble.
Determine where you want to mount the toggle switch. The switch should be close to the old switch's location so that you can simply run the existing wires to the toggle switch.
Locate the existing wires for the old headlight/parking light switch that you are replacing. Disconnect the wiring harness or wires from the back of the switch. Determine which wires send power to the headlights when the headlight switch is turned on. Consult a workshop manual specific to your car for the wiring diagram if you cannot determine which wires are for the headlights.
Determine how the wires are fastened to the back of the new toggle switch. The back of the toggle switch will have a number of attachment points for wires, which will vary depending on the type of toggle switch you are using. These may be blade type connections or even screw type connections that use a screw to fasten the wire in place.
Fasten the wires for the headlights and the driving lights to the toggle switch. This will probably require cutting the ends of the wires and fastening a blade connector to each end. Use wire strippers to remove about ½ inch of the insulation around the wires then attach the wire connectors onto each wire. Clamp the connector securely around each wire by squeezing it with a pair of pliers then wrap electrical tape around the wires and the ends of the connectors fastened to the wires.
Hook up all of the wires to the connections on the back of the toggle switch. There will be a "ground," a "power" and maybe an "accessory" connection. Hook up the existing headlight wires in the proper order, consulting your wiring diagram for which wire goes where. You can also do this, through trial and error, by connecting the wires until the headlights and driving lights come on when the toggle switch is turned on.
Mount the switch to the dash once the wires have been connected and the driving lights and headlights turn on. The switch can be mounted in a variety of ways. Some are simply screwed on. Others need to be inserted into a hole so that a nut can be threaded onto the back of the toggle switch to hold it in place. Make sure that no metal on the switch comes into contact with any metal on the dash as this can create an electrical short and cause further problems.
Test the headlight switch by turning it on and seeing if the headlights come on. The switch should have three positions: one for off, one for the driving lights and the other for the headlights.