I have bought a 96 F250, 351, 8800 gvw with a commercial flat bed. My tail lights work but my signal, break or hazard light on the back both sides don't work. They work on the front, both signal and hazard keep flashing when I depress the break. I have removed the bottom cover on the column to find the MFS (multifunction switch) spoken of in countless threads. I see a large switch attached to the underside of the column about 4"x2" It has some very large (gauge) wires and some smaller ones going to it. It has two torx screws attaching it and one bolt head screw keeping the two parts together. It is mentioned elsewhere that the switch I may need to replace is for the signal and hazard. Is this large switch the one I need to replace or is there one just for the signal and hazard lights? With the front lights working does that mean the switch is working? I have checked with a test light and in both rear lights I have power to the tail lights but no blinking power. They are the sealed lights mounted in rubber with a 3 prong plug and cost about $10 each. I also have no blinking power to my trailer hook ups. I called the auto store and asked about the MFS they said about $70. Would this be the only MFS in there or should I be looking for another one? I am not a pro mech but I am handy at some things reading Wiring diagrams is not one of them. It looks like there are to many large wires going to this switch then it shows going to the MFS on the chassis wiring diagram on page 12-53 in the Haynes 36058.

 

The multifunction switch is the turn signal stalk. The switch on the underside of the column is the ignition switch. Sorry can't help with the rest though.

 

why do you think it is the switch?

if the fronts work it is either a rear bulb, socket or connection.

 

As I said. Why would it be the bulb if I am not getting power to the sealed light unit? Where else would there be a conection where all three operations of the second filiment of the bulb on both sides meet? Do both sides use a comon ground? Do they all go into a junction point somewhere? I am asking, I am not fimiluar with wiring methods which Ford uses. I asked if the switch would not be the problem because it works on the front.