I have a 2006 F150 xlt 5.4 3v. I've owned it since Oct. 15'. In approximately Nov. I lost the rear right brake and blinker light, and then around Christmas I lost the rear left brake and blinker. I also have no rear hazards, but the inst cluster flashes at a normal rate when the flashers are engaged. All running lights work, and 3rd brake light works. Front blinkers work and all other electrical works. Have checked all fuses and bulbs with no solution.

 

Do the turn signals blink at double or normal rate (the hazards won't fast-flash with lights out)?

Pull the covers off the steering column and inspect the wiring harness and connectors for the multi-function switch. Look for pulled pins caused by the harness getting stretched from the tilt column feature, especially if the the truck is regularly driven with the wheel in the low position. Since you just got the truck, it may have been done by the PO.

If there is no evidence of connector, harness, or pin problems, replace the MFS.

 

Since they didn't quit at the same time, I doubt it is a wiring problem.
Start simple - remove the bulbs and check for corrosion in the socket. Ensure the bulbs are good. Be sure to apply a bit of dielectric grease when re-installing. If there is no corrosion present, use a multimeter to check for 12 VDC at the socket, then physically follow the wire while checking for breaks, abrasions, or cuts. At the first connector you come to, measure for 12VDC. Be sure to add a bit of dielectric grease when re-connecting. Continue in this manner until you start to find voltage. Repair the short or open.

 

It's certainly not an issue where a common, single circuit path in single component failed. However, the issue with the wiring harnesses is a well known problem on trucks equipped with tilt columns. It usually pays to check the most common stuff first since it's a relatively easy visual check compared to tracing wiring.

 

So I discovered yesterday that when I plug a 7 pin trailer into my factory harness the trailer lights do not work like mine, but if I put in a 4 pin harness the trailers lights will brake and turn signal, while my truck rears still do not....... I checked the connections on the turn signal switch a while back as it was one of the first things I came across.

 

You never answered the question in post #2.

What does that mean?

You should have said so. We are not psychic, we cannot know what you do not tell us clearly and succinctly.

Was this factory-wired for the trailer harness or was this an aftermarket or previous owner add-on?



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Blinkers blink at double rate. Factory towing package harness.