QuestionDo you have or do you know where I can get a wiring diagram for 56 F100 headlight switch. The terminals are not marked on the new switch nor did it come with wiring instructions.
AnswerI have been working on cars since I was 14 years old (in 1948!), and I have NEVER seen a headlight switch that did not have marking on the terminals. Are you SURE there is no marking? Usually, there will be a tiny stamped letter next to each terminal. If you can find those, give me a list of them and I will see if I can figure it out without looking at it.
Usually, there is a B next to the power inlet, an H next to the headlight wire (both of those are very heavy wires, either 12 or 10 gauge), a P next to the park light terminal and so forth - the tail lights may be marked with a T or an M or an L - usually. The dash lighting may have a D or a G on it.
Sometimes the headlight switch incorporates a circuit breaker - this looks like a tiny bathtub shaped metal box, about 3/4 by 1 1/2 inches long, with two screw terminals on it. If you have that type of switch, the long terminal gets a big heavy wire that comes from your power source- the ammeter, if your truck has one. (I'm here for car questions, not truck questions, so I don't know if your truck came with an ammeter).
The other way to proceed is to use a multimeter or continuity tester to figure out what the switch's internal connections are.
With the knob all the way in, there will probably be no connection between any two of the terminals (the only exception to this would be if the switch includes a circuit breaker).
With the knob out one click, there will be connections from the power input terminal (the circuit breaker outer terminal, if it has one) to the Park terminal, the Tail light terminal, and the dash lighting terminal.
When you pull the switch knob all the way out, there will still be a connection from the power input terminal to the tail light terminal, but the connection to the park lights will disappear. In addition, a new terminal will have a connection - that is the headlight terminal.
If your truck has variable intensity dash lighting, the connection to the dash lighting terminal will vary from a good connection to no connection as you rotate the knob - finding a terminal which you can make change that way (by rotating the knob) identifies the dash lighting terminal.
It's best to draw yourself a diagram to help figure it out (or send the results of the above tests to me and I'll see if I can dope it out).
To get a wiring diagram for your truck, you need the factory Shop manual - which you can buy from any of the automotive literature dealers. I use Ed Faxon at www.faxonautolit.com, but there are many others out there - do a Google search or check on eBay.
I hope this is helpful to you.
Dick
