Looking for some help! I have a 2002 F250 V10. A week ago the AC stopped working so I assumed the charge was low and purchased a kit to recharge (never been recharged). I was unable to recharge because I couldn't get the clutch to engage/compressor to cycle. I tried:
* Jumping the low pressure switch. No luck
* Jumping the high pressure switch. No luck
* Checking for current using a volt meter at the compressor plug with:
* Both switches jumped and jumping (what I think is) the AC relay

Note on the above comment about the AC relay - I can't find out if this truck has a relay for the AC, but there are two relay switches just under the hood right in front of the driver's side. I tried to jump both just to be sure that wasn't the problem. Also as an aside, neither of these relays has power to pin 86. Both have power to pin 30. There is only one 10 amp fuse, and I've put a check light to both sides - that is good.

Nothing I've done allows current to the compressor. I'm out of ideas. I thought that by jumping both switches and both relays, I was basically allowing 12v to go directly to the compressor. Note that I have not been able to get any voltage readings at either pressure switch either. I was thinking this might be a selector switch issue - that seems to be working fine, however in that it seems to change as I adjust it across the options. OR could this be a bad PCM?

After power leaves the 10am fuse, where does it go? I figured a relay (if it has one) or direct to the low pressure switch if it does not. Regardless, it doesn't have power at the fused relay pin (86) as I mentioned, nor at any switches.

Thanks for any help!

 

If you don't have power on the correct wire of the low pressure switch, everything downstream, including the PCM and the clutch relay doesn't matter.

1. Check fuse F28 under the dash. Verify it is actually passing power with your meter, don't assume that the circuit is good just because the fuse does not appear to be blown. HOT IN RUN.
2. Check for power on the Violet wire on the low pressure cycling switch. This is the output of the mode selector switch and should be 1) HOT IN RUN & 2) in any switch position where compressor operation is to be enabled (both conditions must be satisfied).

FWIW, the AC clutch relay is in the same box with the two trailer turn signal relays. Most likely, you were on the wrong relay.

 

Thank you for the reply!

I confirmed no power on the purple wire to the low-pressure switch. Fuse 28 says it's for ETAC Module/Front Blower Relay. Note that I don't have electronic temp control - I have the older dials style. I used a check light and confirmed power on both sides of the fuse. Fuse #10 says it's for the AC clutch - also confirmed power there. So somehow I'm not getting power to the purple wire on the low-pressure switch. Do you know where that gets it's power? Does that go to the fuse box?

I've checked all fuses - all seem to be good. Also responding to your comment on the relay being in the same box as the trailer turn signal relay - I'm only seeing one and not seeing anything related to the AC unit in my fuse description book. I posted a few pics of the owner's manual below. BTW I can't find anything in the owner's manual that shows what the 3 relays are for in the box in the engine compartment just in front of the driver's side firewall.

Thank you again for help. This is making me nuts.




Showing where the trailer turn/relay lives - not seeing anything about an AC relay




Diagram showing RELAY #'s


Fuse 28 - for ETAC (note I have the older style dials - not auto temp controls)


Relay definition

 

Quick update - I put 12 volts to the yellow wire coming out of the low-pressure switch and the compressor kicked on so looks like downstream system is ok. Just have to figure why I am not getting 12 volts to the low pressure switch on the purple wire.

 

That listing is for the fuses, not the relays. Note column heading.

The listings in the owner's manual are not comprehensive. Omissions and errors in the owner's manuals is not an uncommon occurrence.

Power from F28 (WT/VT) to the MODE switch , then out via VT wire to low pressure switch when the switch is in one of the correct positions.

 

Thank you. Your help has been INVALUABLE!! I checked for power at the low-pressure switch socket again - nothing. Checked for power to the purple wire leading to the low-pressure switch socket and have power. The problem is in the plug/socket itself. Again. thank you!

 

So was it in the plug at the selector switch or at the low pressure valve? Did you change the plug on the compressor or on the pigtail? I'm having the same problem and I believe its the actual pressure switch. Female, new to the diesel game so forgive me if I ask any stupid questions.

 

Cherrystein,
I kind of went through this on my 06 last week. 3 weeks prior our trip the A/C worked perfectly. Hooked up the travel trailer to go to the coast and no A/C. I didn't need the A/C at the coast thank God!

After getting back from my trip I did the usual - checked the clutch air gap - it was in spec but pulled the clutch cover and cleaned the oily goop off it using Brake Cleaner. My suction side only showed 10 PSI - naturally the high side showed 10 PSI. Your A/C system will balance out after it sits for a while. You should have at least 50 PSI on your suction side. Even jumping out the low pressure switch WON'T get your compressor to kick in. IF your suction side is less than 50 PSI with the truck off (not running) add your 134A It will take a while to get there. Once you get close to your 50 lbs on the suction side you can fire up the truck - turn the A/C on to it's coldest highest setting and the compressor should kick on. It will continue to cycle on and off until it gets enough pressure on the high side to keep it on. On my 06 it takes 1lb 10oz of 134A or about 2 1/2 12oz cans to completely fill a drained system. Anyway I topped off my system while checking for leaks - soap checking all connections, hose crimps, looking for tell-tail signs of PAG oil leaks. I Found nothing. I let it run for a good 10 minutes and saw no pressure drop. There was obviously a very slow leak somewhere but I sure couldn't find it. After removing my gauge set I soap checked the Low & High side line taps and I'll be a SOB the High Side was slightly blowing bubbles. The High Side Schrader Valve was leaking Damn! O'Reilly's by me had the correct Schrader Valve kit in stock - $18.00 and the special tool to remove & install them was another $16.00 I also rented their A/C Vacuum Pump - it's a free rental service BUT you have to pay $170.00 for the pump in case you don't return it. You bring it back on time you get ALL your money back. If you don't have a real gauge set you can rent that too for another $130.00 again you bring it back on time you get ALL your money back. You will need a real gauge set to check your vacuum and have a place to hook your vacuum pump.

Needless to say I had to SLOWLY (so I didn't lose any PAG oil & make a mess) DRAIN my A/C system, change the Schrader Valves & vacuum the system down. I got about 28" of vacuum, pulled the pump and let everything sit for 2 HRS making sure I had no vacuum leak. Needless to say I had to add another 2 1/2 cans of 134A (I had 12 OZ cans) All said & done it took me all day to get this done because I wasn't paying attention & thinking things through the first time. Live & learn I guess - until the next time when I make the same mistake all over again. My A/C is now Ice Cold again and I'm getting 36 deg air from my A/C vents - according to my Harbor Freight thermal gun anyway.

Don't forget Ambient Air Temperature makes a big difference on A/C pressures so here's a Temp/Pressure Chart for 134A
https://rechargeac.com/how-to/ac-system-pressure-chart

Hope this info is of some help to you.

 

Thanks. I've been blowing f2.28 climate control like crazy. I had intermittent problems before, but then I had a boost leak in the boots so i replaced those and put a new charge pipe in for the hell of it. Also needed new hubs, ball joints, tie rods, tires... Then it seemed like my turbo wasn't working right and I had a coolant leak. Didn't realize how bad it was til i got on the highway and overheated. Puddled in the valley so i figured it was that little blue hose off the oil cooler everybody always talks about. So we pulled the turbo (i thought maybe it was sooted up and the unison ring was stuck or something...looked brand new). When it overheated it melted a hose that was used as a j pipe for an egr delete.



Measured both ends of the hose that was there and kept the metal flange thing that locks it on. Found a hose with the same ends online, checked for a part number, and bobs your uncle. When I was messing with that i noticed one of the wires on the vgt pigtail was broken and solved that problem too. Got it back together and besides blowing a boot on the test drive, lo and behold the damn ac wasnt working. Blower worked until i switched it to ac and then it blow the fuse. I've replaced the blower and the pigtail before, checked every fuse and relay that had to do with ac. Unplugged the blower and compressor, the actuator, and then I pulled the dash to unplug the selector switch (which I hate!) I've replaced the switch and pigtail once already. Still blowing 28. Pulled the schematics, did some perusing on forums. I hooked up the ect3000. Which took me to the wrong place, user error I'm sure. So I took the airbox and intake elbow back off thinking I melted some of the harness or something too. Didn't see anything right away. Decided to plug the compressor back in and see if it threw a code. Got to it from the passenger wheel well and while I was down there saw another plug WITH A VIOLET WIRE that went to the low pressure switch. Unplugged it and tried another fuse and it kept!!! So I found the culprit. Power probed the plug to check for power, which it had. Plugged everything else back in and still the fuse kept. I couldn't figure out how to bypass the switch to see if it cycled so I just figured I'd plug it back in and if the fuse blew id get a new low pressure switch. Well I plugged it back in and it started working without blowing the fuse. I assume that maybe the vibration loosened the pigtail somehow and it was arcing causing the fuse to blow. If it happens again I'm just gonna replace it anyway and hope its a tighter fit. That or a zip tie 🤣 dude, I've been chasing that short for like 2 weeks when I have the time and energy to mess with it. And it was all a loose plug i could get to from the wheel well:/ this is all over the span of a year because there would be an issue and it would sit for a while until it got fixed. Newsflash: diesels are expensive. Anyways, thanks for coming to my Ted talk. Sorry its so long and possibly not pertinent directly, but maybe it will help somebody. You wouldn't believe the things I've found to be helpful on this forum. Next stop the sending unit wire...

Shes still in pieces.

 

Thanks for sharing your findings. I'm sure it will help someone else down the road.

 

I to am having compressor clutch problems, however they have escalated. I tried jumping the low pressure switch with a damn paper clip as noted in many videos and that didn’t do anything for the clutch, it did however render my truck unstartable. I’m hoping the connector is the issue as the fuse under the hood seems to be ok, if I’m checking it properly. Has 12 volts coming to it and the circuits seem open. (Checking the fuse on ohms) is that right? Where else should I be looking? I don’t know too much about these trucks except that I need to learn as they are too expensive to bring to the shop every time something pops up. Any help would be appreciated

 

Both trucks I have owned had intermitted compressor problems. On BOTH....it turned out to be the connector from compressor to switch..... wiggle the wires and see if compressor comes on.