Hello all, I have a 2001 f150 XLT 4X4 with the 4r70w transmission. About a month ago I lost my AC and it wasn't too big of a deal but now it's getting colder and I have no heat either. For whatever reason the #5 fuse which is a 15 amp fuse keeps blowing on me. I have no cruise control, no reverse lights, and no power to my blend door motor. The blower works and the truck heats up no problem and I know the heater core isn't clogged because both lines are getting hot. I unplugged the AC compressor and the condenser attempting to rule out a bad winding or so but nothing. AC compressor reads 3.5 ohms which is just fine. As soon as I turn the key to the run position the fuse just pops. Any and all help is greatly appreciated!

 

5
15A
Speed Control Module,
Reverse Lamp,
Climate Mode Switch,
Daytime Running Lamp Relay,
Digital Transmission Range (DTR) Sensor

One of those items is shorted out or the associated wiring is shorted. The first thing I'd do is disconnect the cruise control disconnect switch on the master cylinder. That was the subject of a recall.

 

Nope, not in the circuit. On a different fuse (F13).

Regarding fuse F05:

Any recent engine, exhaust or transmission work?

Have you disconnected any or all of the named items to see if the short is still present? Does it still blow if the HVAC mode is set to OFF?

 

Haven't had anything like that done. Everything is turned to the off position and as soon as I turn the key it pops. I can't figure out for the life of me what it could be

 

You might have a rodent infestation or possibly chafing wires. Have you started tracing wires?

 

​​​​​​​You sure about that? From the 2001 manual, where I got the above from:

13
20A
Stop Lamp Switch (Lamps), Turn/Hazard Flasher

 

No infestation checked all of the normal areas. And as far as chafing wires go I've never done something like that before and I have no idea where to start.

 

I would suspect the climate control switch. Probably an easy place to start and at least rule it out. Access the switch, there's probably a connector behind it. Disconnect the plug and see if the fuse still blows when you turn on the ignition. If it doesn't then the culprit is likely the switch. if the fuse still blows then the problem is downstream.

 

Yes. See cells 13-9 and 31-2 of the '01 F150 EVTM. Besides, F13 is a ALWAYS HOT fuse.

It's a short circuit, either in one of the loads or due to a chafed, pinched or otherwise damaged wire that is exposing the center conductor to bare metal.

Since it blows the fuse with the HVAC switch in OFF and the shift lever in PARK, the reversing lamps and the "downstream" loads in the HVAC system can be eliminated. If your truck was not equipped with DRL from the factory, that can be eliminated also.

One at a time, disconnect the following and see if the short goes away: You'll either need a supply of fuses or a properly set up multimeter to test. For a novice, the supply of fuses is easier.

Speed control servo module (under the hood).
DTR switch (side of transmission).
HVAC control module.
HVAC Blend door actuator.
[If equipped] DRL Relay #1.

After that, it gets harder.

Related threads, read them before diving in.
https://www.f150online.com/forums/el...g-diagram.html
https://www.f150online.com/forums/hv...5-blowing.html [last post]

 

That was actually one of the first things I replaced suspecting broken internals but it wasn't that either.

 

I have disconnected and tried to eliminate all of those things. The only one I didn't disconnect was the dtr switch because I could not find it and couldn't find any information on it. If you have a link or picture that would be greatly appreciated. Thank you all for your help In this search for heat😀

 

It's hard to miss the DTR switch. it's mounted on the side of the transmission where the shift cable linkage attaches.

Make certain you READ the linked threads. Failure to do so will likely cause you to waste time.

 

Already wanted enough time lol. I read them and they don't seem to be the same issues that I'm experiencing. I have read almost every post regarding this damn fuse and mine just seems unique 🤷 I will try that tomorrow though.

 

They concern EXACTLY what you described experiencing.

 

replace the fuse with a light bulb. power from one side, and short to ground on the other and it will complete the circuit and turn the bulb on. then you go through unplugging/testing sections and if you find the short the light bulb goes off.

keeps you from burning up a ton of fuses on a guess......