Bought my truck (2000 F150, Manual, V6) used with 135k on it. In 3 months I've put 10k more on it and am starting to run into a weird A/C problem.

Driving to one of my clients, everything was working fine. When I left there was no A/C. I checked coolant, fuses, etc with no luck. We had a bit of a cold-snap and I also found out my heater didnt work. Air comes out of the vents, but it's all panel air, regardless of temp or control settings.

Took it to a mechanic who said the high-pressure switch was dirty, he cleaned it and the A/C worked at the shop. The moment I left the exact same problems started happening again. It's been back to the same mechanic, and today he tells me that the a/c clutch is drawing to many amps and shorting it out, at which point the PCM tells it to goto hell. He can get it working by resetting the computer, however, the moment I put it in gear it stops working (a/c, heat, all of it). He was able to put power directly to it and it run with no problems.

To me (very little mechanical knowledge) it seems like power, or the condensor. The mechanic said that the heat going out isn't related at all, which makes no sense to me because it's happened there in his shop where the heat will only work if the a/c works. Hes telling me I need either a new clutch or a new compressor altogether. Quoted me 300 and 1000 for each respectively.

Does any of this sound right or has someone else had a similar problem?

Side-Note: The morning of the day when the a/c initially broke, my car turned off suddenly while driving. I was in gear and driving down the road like normal. I popped the clutch, turned the key and it started right back up. Also, cruise control seems to have stopped working and the eft blinker. If i hold the lever down (like push an extra 2cm) it comes on and works. It is sporadic.

 

Check the FAQs above and see if any of the described symptoms match your observations.

 

Looking through the FAQ, the only thing that seems remotely similar is the "loss of cooling while accelerating/cruising" or the "No cooling, No engagement of compressor clutch" None of the above mentioned FAQs mentioned anything both heat and A/C related, and that's the only reason I am not leaning towards the clutch/compressor. My understanding, and experience with an 01 Explorer, is that the heat should still work regardless of the A/C working. If the blend door loses power/functionality when the A/C stops then I guess that would explain the loss of heat as well. Would the PCM kill power to everything HVAC related?

If the general consensus is that my mechanic is correct and the A/C clutch is pulling to many amps, then I'll get that replaced.

 

Indicates a loss of temperature control (blend door). Stripped ****, stuck/non-functional actuator, etc... This function is independent of the clutch's operation.

Nonsense. The PCM has no way of know how much current the coil is pulling. The series circuit of the mode switch, low pressure cycling switch, and the high pressure cutout switch form an "AC Demand" request to the PCM. The PCM, provided current parameters do not preclude it (wide open acceleration, for example), then energizes the WOT relay which supplies operating power to the clutch coil. The coil is supposed to stay energized via this method as long as it is enabled by the operating mode and the pressure in the system.


I suspect you have two simultaneous faults and the mechanic can't sort it out.

 

Would it still be something like you mentioned above if when the clutch is enabling everything works great? If I turn on my A/C right now, the clutch doesn't enable and I get nothing except panel air through the vents. If I "clear" out the computer and restart the A/C, everything works until i start rolling in gear (rolling with just the clutch kicked in while in neutral will keep everything working).

I appreciate all the help. I think this weekend I'll take it to somewhere like Midas to have them diagnosis it (not necessarily fix, since they are way over-priced).

 

tl;dr: Don't trust unknown mechanics and check your fuses.

Got it fixed. After everything it appears to have been a fuse :\

I am not sure what the original problem was (very well could have been the high pressure switch as well as the fuse) but the eventual fix was replacing fuse #5(Speed Control Module, Reverse Lamp, Climate Mode Switch(bingo), Daytime Running Lamp Relay) underneath the dash. From what I can gather the mechanic replaced that fuse with a 30amp amp fuse, which also blew. Once I replace the 30amp with a 15, everything worked.

Story on how I found out:
I went to a store today to pickup a birthday gift for my brother and as I was backing out the car behind me pulled up to let me know my reverse lights were out. So after I got home I decided to read each fuse description, rather than just skimming for what I was looking for, and check the ones that seemed relevant.

In my original posting I mentioned that my cruise had gone out, but couldn't be certain if it was at the same time as my a/c, and when I looked for "cruise control" fuses, I found nothing. Well, reading the fuse descriptions, I realized Ford called it "Speed Control". So I checked all of the fuses related to speed control, pcm, and a/c. The #5 fuse had a 30amp, non-stock fuse which was blown. I replaced it and viola.

I knew the mechanic was crap when I took it to him the first time. He told me my battery was bad because he had to start it from the solenoid twice. He had it running when I arrived so I just drove it straight home. Once I was home, I tried to start it and got nothing. I checked the fuses then and realized he had taken out and left on the floor mat my clutch switch fuse (#20). Replacing it started the truck right up.

Experience gained? Never trust a mechanic you've never worked with before, and also do your due diligence when it comes to checking the things that should be quick, easy fixes.