I have a '96 National Tropical motor home on a Ford F 53 chassis. I tow a car and run the signal lights off from the factory mounted connector at the rear bumper. The other day I took it out on the road, without tow, and noticed that the cruise control was not working. On further inspection I found that the brake lights do not work. The four way flashers do not work in the back (only) and though the turn signals do work in the back, they do not work in the front or on the dash. AND I am able to take the transmission out of park without stepping on the brake. All the running lights seem to work and all the fuses appear to be ok. Any ideas on this one would be appreciated.

 

The one common thing to the brake lights, cruise, rear hazards, and shift lock is a power wire that comes from the brake switch on the pedal. I would get a testlight or voltmeter and get under the dash and find the brake pedal switch. There should be a lightgreen/red wire there. This is the hot wire feeding the switch from the fuse box, fuse #9, 15 amp. You should have power there all the time. If it doesn't, check the fuse again.

If you do, then find a lightgreen wire leaving the switch. This should have power on it when you push the pedal. If it does not, then the switch looks like it's bad.

 

Gotta be a blown F9 or open in that circuit.

I'd suspect the shift interlock is an additional fault. It should engage via F7 when the ignition switch is turned to RUN. It should not release until the brake pedal is pressed, feeding F9 power to the release portion of the actuator.

The cruise requires F9 power regardless of the state of the brake switch and its circuit.

F9 also supplies the electronic flasher, but only in HAZARDS. In the normal position, the flasher is supplied by F7.

Steve

 

Thanks to you both for the leads. I will check them further today. It is so hard to get under the dash in this motor home.......... may need to buy a monkey. Will let you know. Thanks again.

 

One more question..... Where do I find the "shift interlock"? I suspect it is located on the transmission some place. That may be the easiest place to start since getting to the brake switch is almost impossible on my coach.

 

The shift lock actuator is located down low on the driver's side(left side) of the steering column. It's actually mounted to the steering column.

It sounds like it's going to be just as hard to get to as the brake switch. Logically, there is no point looking at the actuator yet. The actuator is at the end of the line as far as the circuit goes, and since so many other circuits are being affected, the problem logically is further up at the beginning of the circuit, such as the fuse box or the brake switch, or a wiring problem in that area. Make sure there are no wires hanging down where they may have gotten kicked around by your feet.

 

I have since found what you said to be true. I am suspecting the brake switch however there are so many problems here, which I feel are related, I wish I had a diagram (schematic) for the '96 F 53. With a diagram I might be able to locate a common denominator here. Anybody know where I might get one?

 

Here's a couple diagrams:
If you need something specific,let me know.

 

Though I haven't yet found that common denominator, I am studying the very helpful diagrams you attached. They seem to have all the circuitry I am interested in - at least as far as I can tell now. Thanks for your help.

Is there a manual, with diagrams, available, on the market, for the '96 F53 pre-builder chassis? Might be handy as I go forward with this aging beauty.

Thanks again for your sharing and efforts.

Motorcoach

 

F9 circuit is the common denominator. I thpought I made that clear... The interlock is probably an additional fault

(Is there an echo in here?)

The factory service manual includes the F-53 chassis.

 

Found the problem and want to post the results to help those with similar problems. It turned out to be the "multi-function switch." Can't explain what related all the problems other than the fact that the coach builder must have wired some of the Ford chassis wiring a bit different from the schematics. I took the switch apart (if you don't know what you are doing, plan on buying a new switch - it is complicated - but then I guess you don't have much to lose) and found some bad and sticking contacts. Polished the contacts, cleaned and re-lubed the inners and re-assembled. Everything works like a champ. My experience says that the contacts will probably go again but when they do I will know exactly what the problem is and will get a switch on order. Doubt they are cheap.

My thanks to all who helped with their suggestions........ especially "Cuda_jim" who attached some very helpful wiring diagrams.