Hello everybody, I have a 97 f-150 with the 4.2 that keeps blowing the fuse for the ac. AC has worked great since truck was new and I have never had to touch it,however it just quit working last week. I found a blown fuse under the dash at the fuse block. I put a new one in and it works great for about 30 seconds and then blows again. The compressor kicks on with new fuse then fuse blows and compressor will not kick on. My question is where should I start looking for my problem? Are there any steps I should take to find this? Any and all information would be helpful. THANK YOU JIM

 

What fuse is this? Is this the one that controls the blower, too?

Try disconnecting the compressor clutch and see if it blows the fuse again. If it does, you might want to look into replacing the blower motor itself. They DO go bad, and dont buy one from the junk yard.

If it doesent blow the fuse again, you could be needing a new clutch coil.

Good luck.

 

Did a little testing. I unplugged the 2 wires at the compressor clutch and checked the ohms at the clutch coil,reads 4.0 also ran the truck with the wires unplugged and the fuse still blew. So I am thinking the clutch and compressor are fine. I do not know what else if anything runs off this fuse. The blower still runs when this fuse is blown. Anybody know what else I could check? THANKS JIM

 

The blower is on a different fuse.

4.0 ohms is okay for the coil's resistance.

Turn the HVAC MODE switch to OFF and see if the fuse still blows. Need to isolate which of the load circuits is shorting to ground.

Fuse F5, in addition to powering the clutch coil, also feeds the blend door actuator, the speed control amplifier (unplug it and retest), and the backup lamp circuit.

I'd probably look at that speed control module connector first. They're known to fail....

Steve

 

Yeah, 4 ohms is fine for the clutch. I was making assumptions using my own truck for the experience.

Does it blow the second you start it up after replacing the fuse, or does it wait awhile?

If it continues to act up, be sure to check the compressor clutch from each of the connecton pins to ground and see if there is any continuity there. Shouldn't be any.

 

Thanks for the help steve,Is the speed control module and speed control amplifier one and the same? Could you please tell me where they are located? THANKS JIM

 

Yes, under the hood. Locate the throttle actuator cable and follow it back to module.

Steve

 

Steve,are you talking about something to do with cruise control. I do not have cruise control. JIM

 

Then we can eliminate that as a possibility.

Steve

 

Steve thanks for all the help. I think I have it down to being the back-up lights as my problem. Everything else works good until I put it in reverse and then the fuse blows. Where would be the best place to look for a short? Are there any areas that are known to go bad? What would be the best way to find a short? I am not very good at this electrical stuff but I would to get this fixed. THANKS JIM

 

Pull the backup lamp relay from the extra relay box under the hood to eliminate the trailer circuit. That relay box is undocumented in both your owners manual and int he service manual. The backup relay is the one closest to the firewall and to the driver's fender (between the big relay and the blank space).

I'd look first at the backup bulbs and their sockets. Perhaps a corroded or melted connector or socket.

Steve