Howdy. I have a 2001 F350 Crew Cab that the left rear turn signal / brake light does not work. Replaced the bulb, no change, switched the bulb housing - it worked in the right side, so that's not the issue. The parking/tail light works, so there should be ground. I pulled out the multifunction switch, cleaned the contacts and replaced. Still didn't work. I switched the orange /lt blue wire (right side) with the green/orange wire (left side) at the multifunction switch and it the right turn signal worked with the left front, so the multifunction switch should be good. Where else does the green/orange wire go from the multifunction switch along its route to the left rear tail light? What else could it be. I assume something must be grounded/worn thru along the green /orange wire route to the rear. Is there a way to test continuity along the wire? Is there another fuse or switch that the green/orange wire goes thru?

Thanks.

 

I would start by looking for voltage at the bulb. Use the bulbs ground and a good ground point to verify the ground. Check the trailer plug too.

If you have long enough leads, or an extention wire, you can check the ohms on the wire from the switch to the bulb. Just be sure that the bulb doesn't have power going through it. However I doubt there is a diode between the trailer plug and the truck's bulb, so you should have continuity across them.

 

You could look in the fuse box under the hood, at fuse #1, 7.5 amp. The diagram I have shows the lightgreen/orange wire going directly to the left rear light. But along the way there is a splice, and another lightgreen/orange goes up and feeds this #1 fuse in the fuse box under the hood. I am going to assume this is for trailer towing if you have this fuse. You could put the signal on, and then see if you have blinking voltage at this fuse. The fuse for the other side is supposed to be fuse #3.

If you do not have anything at the fuse, I would back up to the multifunction switch again, and take a testlight(not a voltmeter) and probe the multifunction switch and see if you can get the testlight to blink there at the steering column.

 

The test light blinks at the multifunction. I could not get any reading at the fuse. I checked the trailer plug and nothing on the left turn, tail and right turn ok. However, I do not have a ground at the plug (the ground pin was not registering as a good ground). I checked the ground at the lamp and it was good (using the tail light). It appears as though someone has done something interesting at the trailer plug to wiring harness connection and spliced into the green/orange line directly into the trailer plug yellow line. I disconnected this and the trailer harness (at the factor connector?). Still just get the quick flash and no light.

Thanks,

 

Well, I found the problem. Way too much troubleshooting for a simple answer (isn't it always that way!!). In the wiring harness connections under the master brake cylinder/brake fluid container somehow (maybe a mouse chewing) the green/orange wire was rubbed/broken thru (and a few more wires as well). I will check with the dealership tomorrow and see if they sell the connector with pigtail, or can the connector be disassembled and a new wire pushed through? I guess I could also jump the connector, that would probably be easiest. Thanks for the help ReAX and Franklin2. If needed I can post pics of where the problem is.

Thanks,

 

Motorcraft has replacement pigtails, as should standard and delco. You'll break a couple of tabs trying to reuse pins in the pigtail, but it is possible to disassemble and rebuild it.

 

So I jumped the green/orange wire over the connector in the engine compartment, reconnects the tail light wires in the back, and....

brake lights work, but flashers and blinkers stopped. In fact I get no hazard lights. I have not had a chance to check the flasher fuse - any other ideas?

 

But the flashers work on one side like they did before if you do not jump the wire? If they do not work at all now that you have messed with the wiring, I would say you jiggled something else, or possibly a wiring error.

 

Found a blown fuse. For now everything works. Thanks for the help!!