How you all doing. Sometimes when I put my truck into drive, reverse, park, anything, the fuse to the instrument panel will blow. Its the small 5 amp fuse (i forget the number). There will be a month where it will do it three times a week, to a month where it doesnt do it at all. Its a sporadic thing, and it only does it when I shift into another gear (truck is automatic). I'm assuming it could be some sort of a short, where at though? Where do I start?

 

Do you have a schematic and do you know how to read one? That's where you start, but you probably wouldn't be asking where to start if you had a schematic and knew how to read it. You also need a meter. Analog is OK, but a DVOM would be better. Start at the fuse. What circuit is this? What functions does it control? You are looking for a pinched wire or bad insulation touching on ground(metal chassis) or a motor that has a problem on this circuit that is drawing too much current. It's unlikely that it's a motor because motors usually draw more than 5 amps which is what you say is blowing. Also keep in mind that fuses blow for two reasons. There is the DEAD SHORT and there is also the OVERLOAD. The dead short will blow the fuse as soon as you plug in a new fuse(unless the wire that is touching metal is moving around) whereas the overload will happen slowly as the current load increases to the' point that it excedes the fuse rating and then poof. If you look closely at the fuse after it blows sometimes you can tell if it blew due to a short or an overload. If it was a short you will see some black soot at the point on the fuse where the conductor melted. If there is no soot there this usually means it was due to an overload. You can use this information during your troubleshooting, but maybe I'm giving you too much information. This can be a hard problem to find. You look at the schematic and figure out ALL of the circuits that are controlled by that 5 amp fuse which ain't much considering 5 amps is quite low. At least that is in your favor. I would put in a new fuse and start wriggling the wires on the 5 amp circuit until the fuse blows. If it blows as soon as you plug it in the wire is already on ground potential. In that case you need to use a resetable circuit breaker in place of the 5 amp fuse or you'll go broke replacing fuses. If the fuse blows immediately you will have to disconnect all of the connectors going to all of the devices on that 5 amp circuit. You then put in a good fuse or circuit breaker and plug in one device at a time on this circuit until the fuse blows or breaker trips. When it does you have found the BRANCH of the circuit that has the SHORT. You then concentrate on that individual part of the circuit and ignore the rest because you have now found the area where the problem is. You'll need an assistant to help you find out exactly where the fault is. They will either have to watch the meter or some lite bulb on the circuit as you giggle the wires around trying to get the fuse to blow. When the fuse blows you start looking for a wire with bad insulation that is touching a metal surface somewhere. This can be EXTREMELY difficult to find. What if it behind your dash board. That means a lot of work. Have you done any modifications on this vehicle lately? That would be one place to start looking for a bad wire.

 

You have a worn wiring harness where it enters the shift lever.

Pull the column shrouds and repair with electrical tape.

As always: IDENTIFY YOUR TRUCK in your post. Provide explicit details about WHICH fuse is blowing, etc.

Steve

 

eallanboggs, thanks for the long post and great infor it really helped.

projectSHO-the column shrouds are exactly what?

and im sorry for not specifying it, its a 97 f150 4x2 automatic

 

I beleive Project is talking about the plastic covers that cover the steering column.

 

Apparently this is a problem other Ford owners have already had. Pull the cover off of the steering column and look for a bare wire touching a metal surface. Remember that plastic is non-conductive so a bare wire can touch plastic all day long and not cause a fuse to blow. You could also have two wires touching each other instead of one wire touching on ground. The steering column sounds like a real good place to start considering which functions are being affected. I would look for something that moves(key switch area, shifter arm area) that would pinch a wire or wear the insulation off of a wire. Right now you're fishing for the problem. Once you hook the fish you can cook him.

 

very well said. i completely understand. thanks for the big help ill do that when the weather gets warmer out, or ill do it in a garage. ill look for what you all told me to look for, and im sure ill be okay.