My 2006 F-350 Dually Powerstroke has a speedometer problem. When hot, the speedometer stops working. I've taken the problem to the dealership 6 times for repairs and it still does not work when the truck is hot. They've changed the instrument cluster, speed sensor and the wiper motor as possible repairs. I've noticed that under the truck the dealership repairmen spliced two wires to from the rear to the engine compartment. I believe the speed sensor is still bad.

SOURCE: Instrument cluster not working and truck wont go

I had the same issue with my 2002 F250 7.3 L. The overdrive switch was shorting the circuit due to exposed wires in the steering colum. I replaced the switch and resolved the problem.

SOURCE: Ford Escort Odometer Not Working

these can also be caused by a bad alternator

SOURCE: How do I replace a blown bulb in the speedometer

difficult to reach. you will have to reach behind the cluster and remove the old one. They will, should twist out, turn 1/2 turn?

SOURCE: No instruments, guages or lights.

there should be a fuse panel somewhere in your engine compartment ,check those

SOURCE: Hayne's Manual for 1986 Taurus

if its a manual cable you just unscrew from transmissionwill be at your gearbox and remove all cable ties holdinding outer cable might give ya enough slack to remove from dash end