My A.C. compressor doesn't have power to it on a 2000 f150 , I checked at compressor plug with a VOM meter . I changed out the heater core last winter , hoping it is just a relay or fuse but the maual doesn't specify a fuse for the ac ????

 

Found fuse & relay under hood in the power distribution box & both apear to check out to be fine . still can't find problem with power source to compressor

 

The low pressure switch removes power from the clutch when the freon pressure is too low and I think there is a high pressure cutoff on the discharge side. Need to do some more trouble shooting.

 

you are correct , I forgot to explain that the truck has a full ac charge just a lack of power

 

Disclaimer: I do not have my schematics with me this week as I am traveling, so the following should be corrected by anyone who has them in hand.

Starting around 99 MY, Ford changed the circuitry so that the output of the HVAC control, whether manual or EATC, was fed in series through the low pressure cycling switch and the high-pressure cut-out switch back to the PCM. The PCM, based on its programming, recognized this "AC request" and, if conditions were permissible, then energized the A/C clutch relay in the under-hood box. The relay then switched fused battery power to the clutch coil to energize it. Sorry, don't have any of the fuse ID numbers memorized....


IOW, a blow fuse, a bad relay, an open cycling or HPCO switch, or a PCM fault can all cause a lack of power to the compressor clutch coil.

I'll be back to my main server late Sunday or Monday. If needed, I'll get the schematics available if still needed.

 

Thanks projectSHO89 for you're reply , I have the schematics for the ac system but am having a hard time finding the physical location of the low pressure swirtch & the PCM

 

The low pressure switch is probably on the accumulator can. The PCM is in the firewall.

 

i have the exact same issue. I have a 4.2 v6. No power to the ac compressor. I installed and shimmed a new ac clutch. bearings on old one were toast. On my vehicle the fuse is #5 a 30 amp fuse and the ac compressor relay is 204. Low pressure switch is on the accumilater and high pressure switch is on drier. Both are within 9" of the pressure caps. Took a wire and jumped both high and low switches and even when they were jumped no power to the compressor. Have a full charge of r134 as well. 40 on low and 250 on high. I am told that the dash control panel switch might be the issue. The switch for panel ac and max ac all work though. I am told the leg on the switch that gives power to the compressor might have burnt. Will try and get a new one or go to pull a part and try it. Any ideas from anyone else would be appreciated thanks

 

1) Next time, please do not hijack an existing thread and avoid resurrecting old, stale ones.

2) We need to know the *year* of your vehicle since there are different circuit configurations.

3) The "accumulator" and "drier" are the same thing.

 

I have a 2000 f150 with a 4.2 v6. I just had the compressor clutch go out and burn a bearing. I replaced the ac compressor clutch and am told it was shimed perfect. With that in mind got a new charge of r134 from a mechanic. 40 on low side and 250 on high side. Worked awesome for about 5 days and then all of a sudden cold air stopped blowing cold air. Dash selector seemed fine. Took to a small mechanic shop and they jumped both high and low pressure switches. Still no efn power to ac clutch. Mechanic checked all grounds to compressor and it was fine. He added 2 # of r134 and all was ok for the moment. However there is no power to the ac compressor. It is hot and i need to get it working asap. I went and got a new used control panel set from the junkyard but still no power to the ac compressor. iI am really stumped here. Does anyone have a suggestion on the next step or what this could be. Also a new relay and fuse were swapped to isolate that issue. thanks

 

What exactly does PCM stand for? Is it Powertrain Control Module? I am having the same problem with the ac compressor on my 2000 F150. No power to the compressor. I had the heater core replaced last winter then the blend door went out and I replaced it. AC was working fine and then the next time I got in a week later the AC was not working. Compressor not kicking on. My husband tried tracing power to compressor and has it until he gets to the plug that goes into the compressor. Help! This is actually my sons truck and we have spent plenty of money on it in the last year including transmission rebuild and want to have an easy fix that we can do here at home. Where is the low pressure switch located exactly and what does PCM stand for and where is it exactly. Thanks!

 

I have a 2005 F150 5.4L. I have no power to my a/c compressor. I have checked all sensors, relays, fuses and jumper wired the high and low switch with no positive results. The high side press or switch has voltage even with the a/c turned off. Is that normal?
The scanner said "the air conditioning clutch relay primary circuit malfunction test fails when the powertrain control module grounds the wide open throttle air conditioning cut off circuit, excessive current draw was detected on wac circuit"
Where do I need to look? What do I need to do? I'm a mechanic by trade and am at a loss.