I'm having a problem a 98 F-150 4.6 V-8 automatic transmission 85K miles. About 6 months ago the guages on my instrument panel went dead. It turned out to be a blown 5 amp fuse (#29). Replaced it and it worked fine for a while. The same fuse would still blow every now and then. After a little checking it seems to be occurring when shifting out of park (P) into reverse (R). It would sometimes also occur when shifting from D to N to R.

Started blowing the same fuse at a more frequent rate but still was lasting about a week. I now blows the #29 5 amp fuse almost every time shifting from P to R. If you shift from P through R before starting the engine it will work. The safety interlock is still working (it won't start in D or R). There is never any affect on transmission performance or shifting. My question is does this sound like the Transmission Range Sensor (TRS) is bad? How difficult is it to determine if its bad? How do you change it out and does it require some calibration?

Thanks

 

It's not the TR Sensor.

Fuse 29 - protects the following circuits:

-Autolamp Module
-Instrument Cluster
-Transmission Control Switch
-Brake Warning Resistor/Diode Assembly (With Rear Anti-Lock Brake System)

Does the Overdrive ON/OFF switch at the end if the shift lever work alright? I found that when the wires inside the lever that lead up to the switch frayed, they would occasionally ground. This would blow the fuse for the instrument panel.

I'm thinking that when you move the shift lever, a bare wire inside is touching metal and blowing the fuse.

 

When the fuse is replaced and guages are working the O/D light will turn on and off. It doesn't work when the fuse is blown. How do you disassemble the gear selector to check the wiring?

 

The first step when working on anything electrical is to disconnect the negative battery cable so you don't blow a fuse or kill yourself.

Pop off the O/D switch at the end of the switch lever and disconnect the 3 wires (keeping track of where each is connected).

Next you need to remove the gear shift lever: Put the truck in 1st or 2nd gear and you'll find a pin at the base of the shift lever that holds it to the steering column. Pull the pin out with a plyers. It may be covered with a leather boot that has to be cut or pulled back to gain access.

When you remove the shift lever, it will expose the 3 wires leading up to the O/D switch.

 

I'll give it a try this evening when I get home. Do I just pry out the O/D switch at the end of the switch lever? Did you have to replace the wires or was it the actual switch? Is this a common failure for the trucks? I found the followin reference for 99 superduty

"6.17 - Instrument Cluster Failure -SSM#12143
1999 Super Duty with 4R100 Auto. with blown fuse #19. Overdrive cancel light flashing and instrument cluster guages inoperative. This may be caused by wiring concern. Inspect for the overdrive wire (purple with orange tracer) to be cut by the bracket that attaches the shifter to the steering column. The wiring is enclosed in a rubber sleeving. Inspect the area where the wiring curls around the bracket and repair as necessary"

I believe that its in the motion of moving the gear shift lever when changing positions that is shorting out the fuse. It blew the fuse yesterday evening when I shifted from D to 2. The gear shift lever has to be pulled forward to move to that position. You can shift from D to N without having to pull the lever forward.

 

This is fairly common and it is the wires, not the switch. When my wires frayed, I soldered in 3 new ones because the original wiring simply wasn't long enough.

To remove the O/D switch, just pry the cap off the button with your finger nail. It's all very straightforward and logical.

 

I finally had a day that I could check it out. It was just as AjRagno suspected, the insulation on the wire was worn away, exposing bare wire. You need to remove the key switch in order to pull off the top of the steering wheel cover. I coated the exposed wire and put some electrical tape over it. I didn't want to pull new wire and thought I would give it a try. Put in a new fuse and it seems fine - no more blowing fuses when shifting to reverse. Thanks again man.

 

That's pretty cool

My experience with this is that the wires fray at the base of the shift lever, not actually under the steering column cover. Good to know