Stuck in park and blowing fuse

[Brad B]

96 7.3l keeps blowing dash fuse #13 (15 amp). If I put in park I have to replace the fuse to get it out of park. Even with it in neutral, as soon as you touch the brake pedal the fuse blows. I've unplugged the VSS and ABS module and still get the same results. Obviously a short somewhere but I've reasearched common problems for 2 days now and can't track anything down. Otherwise it drives fine with proper reading on speedometer and such. Just no brake lights or hazards, etc. when that fuse blows. Any ideas would be appreciated!

 

[KRISTOLSON]

Try disconnecting the brake light switch by your brake pedal and see if it still does it. That will help tell if the short is on the brake light circuit or on the cruise control stop circuit. As for finding the short, it usually sucks. If it is on the brake light circuit start with the visible wiring I guess like near where the switch is on the brake pedal, as well as where the trailer light wiring tees off from the main harness in the back. Also, if your tranny has been out 4 times it stands to reason that the wiring could be pinched or rubbed near there. If you have a brake controller wired in you might want to inspect those wires. If it is on the cruise control circuit there are not a lot of exposed runs of wire, likely a bad module maybe? Or a wire inside the steering column? Sorry I don't have an easy answer for you

 

[Brad B]

Thanks for the reply. I already took that switch off and bypassed it. Same thing happens, soon as you make that connection on the brake circuit the fuse pops. Also tried disconnecting the ABS module in case it was bad=no luck. Disconnected the 3rd brake light assembly=no luck, too out all the brake/tail bulbs thinking it could be a shorted bulb=no luck and all bulbs checked good on a meter. I parked it and about 10 min. later went to drive off and all this started, can't imagine how it would happen so suddenly. Next plan is to start tearing apart the trailer pigtail wiring. Nothing seems amiss there but it's the most logical since it's exposed, everywhere else is in wire loom and under the dash is a maze of wires that all look fine with no pinch points.

Maybe someone will see this and come up with something I've missed.

 

[DaveBen]

Have you, or some one else, spliced into the wiring harness in the frame going back to the tail lights?? It sounds like a problem outside of the cab to me.

Dave

 

[Brad B]

Nope nothing new there Dave, it's had the trailer wiring on it since i bought it. I'm about to go out and check the wiring on the master cylinder. From what I've been reading it could be a short there on the cruise deactivation circuit. Past that I'm going to have to assume it's in the wiring on the rear. We were experiencing several wet days so maybe some moisture made a short in the trailer wiring.

I hate electrical mysteries!

 

[BIG JOE]

IF.. it IS the Cruise Control de-activation circuit.. there was a Recall on that. You might wana check with yer local Ford dealer ? Don't know if it goes as far back as 96.. but it's worth a Shot ?

Also.. with the wet days you've mentioned. drop the in-cab fuse block down.. and check for moisture ? These trucks are known to leak water in, from the D-side windshield area.. it migrates down the wiring.. into the fuse block ? (a Hair dryer will dry things out ?)

And.. check the under hood Power Distrabution Box for moisture too ?

Joe

 

[Brad B]

Thinking you might be onto something there Joe. I went and disconnected the cruise control sensor on the master cylinder, then put my amp meter on and everything looked normal. Started plugging compenents back in and amps stayed normal. Ended up with everything back on incl. the cruise control sensor and everything still checked good. Cranked it up and shifted out of park like nothing had ever happend. So.... the only thing that has changed is that is has sat in the driveway for a week without any rain so maybe something dried out. I have had a small leak around the windshield but it usually drips down on the passenger floor from near the headliner. No evidence of any moisture in either fuse box. But it's something that may rear its head when it rains again and I guess we'll find out then. I just have to stock back up on 15 amp fuses just in case!

Thanks for the input guys!

 

[Tbar]

Take your trailer brake plug apart. Not unusual for a wire to loosen up/pull loose inside the plug.


Tbar