Need help with compressor clutch.
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Senior User
Joined: Jul 2001
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From: Walterboro, SC
Need help with compressor clutch.
My AC worked last year, but between then and this spring it has broken down. Here is where I'm at. The compressor clutch is not engaging at all. When you first start the truck in the morning the AC will only stay cool for a couple miles then it just turns to vent temperature. I checked the resistence at the clutch (0 ohms). I wired the clutch straight to the battery and it clicked on fine so the problem must be a switch somewhere. There's my problem, I don't know much at all about HVAC and what kind of switches I should look for and how to check them. Any help is appreciated.
I have another problem also. I noticed a huge lump in the wiring harness about six inches from the compressor connector so I took it apart wondering what was there. In the process I broke the wires to these two things off. (resistors?)
What is this and have I messed something up? I have a picture of these connections in my gallery.
I have another problem also. I noticed a huge lump in the wiring harness about six inches from the compressor connector so I took it apart wondering what was there. In the process I broke the wires to these two things off. (resistors?)
What is this and have I messed something up? I have a picture of these connections in my gallery.
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Joined: Apr 2004
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From: I live in Calif. near S.F
If you put 12volts to the clutch it well click, and your right about a switch, check your lowside pressure switch you should find it on your lowside hose ,unplug the switch ( eng. running ,a/c on) and jump the plug over if the clutch unit turns you may need to replaces the switch, or charge your system ?
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Joined: Dec 2002
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From: peoria, az
If you didn't break the splices on your wiring, I'd just tape it back up(neatly). Your low-press switch should be just before the lines go into the cab. Looks kind of like an oil sending unit. I believe that you have found the right one. Should have 2 wires. If you short them, then you comp should kick on and it should blow cold. You may want to have your pressures checked, your system may be a little low causing the switch not to work once it starts cooling and the pressures drop.
Senior User
Joined: Apr 2004
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From: I live in Calif. near S.F
That sounds like that switch , around your a/c dryer ,two wires, like i said , if it cycles when you jump it ( eng. & a/c on) try the switch, note when you replace the switch make sure to replace the "o" ring too, again like i said it may also need freon.
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Senior User
Joined: Jul 2001
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From: Walterboro, SC
Thanks for your help. Unfortunately I cannot check the switch until I get my wiring harness fixed because I can't have current flowing back through my electrical system when the clutches off. A fella down in electrical explained the wiring to me. What I have there is a diode that prevents the stored electricity from the clutch coil from flowing back "up" the electrical system and frying various parts.
I checked one junkyard, an auto-electrical shop, and the Ford dealer, but nobody had the diode. They can get the connector but not the diode system. There is a computer store in town that an older fella runs and I hope he will fix it for me. I'm sure he runs into things like this with computers.
Oh, the outer shell of the diode is shedding some wires so I wouldn't want to just re-solder the connections and let it go. I need a new setup.
So, until then I can't check the switch. I believe it is probably the problem though. Thanks for your help! I'm slowly learning how HVAC systems work and the various parts.
I checked one junkyard, an auto-electrical shop, and the Ford dealer, but nobody had the diode. They can get the connector but not the diode system. There is a computer store in town that an older fella runs and I hope he will fix it for me. I'm sure he runs into things like this with computers.
Oh, the outer shell of the diode is shedding some wires so I wouldn't want to just re-solder the connections and let it go. I need a new setup.
So, until then I can't check the switch. I believe it is probably the problem though. Thanks for your help! I'm slowly learning how HVAC systems work and the various parts.
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Joined: May 2004
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Thanks for the info!! I had the same problem, worked last year but blew warm air this year. I replaced the clutch cycling switch and it's FREEZING now!! Only cost $17 at Auto Zone....$23 at NAPA.
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Senior User
Joined: Jul 2001
Posts: 491
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From: Walterboro, SC
I got the wiring fixed and checked the switch. Jumping the terminals on the switch at the condenser does not click the AC clutch on. The only other switch I can see that may be related is a small canister above the wheel well that has a vacuum line running to it. I took a few pictures of my setup just in case you're not familiar. Thanks for any help.
http://www.clubfte.com/users/nothing...279_Large_.JPG
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Senior User
Joined: Jul 2001
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From: Walterboro, SC
Sorry, I must of had a brain cramp yesterday when I posted...I jumped the switch on the accumulator not condenser. Anyway, that still didn't switch the clutch on. I'm pondering wether I should just buy a recharge kit or take it to an HVAC technician?
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From: peoria, az
I'll have to look around and see if I have a diagram. If you have power at the low press switch then, I believe your trouble lies between there and the clutch. When you bypass it, check to see if you get 12v at the clutch.
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From: peoria, az
O.K. Ben,I don't know if what I have is exactly like yours but, it should be close enough. After the power leaves the low pressure switch, it goes to the WOT (wide open throttle) relay. Basically, you will have a red wire at this relay that is powered by the EEC relay, you will have a org-lt blu(?) wire that will energize it from the PCM. On the other side of the relay, you should have a pink-lt blu wire that comes from the blk-yel from the low pressure switch and then a blk-yel that leads to the clutch.
This relay is to shut off the clutch when you put your foot in it so it should have continuity normally. Look to see if you have power coming and going on the switch/clutch side.
This relay is to shut off the clutch when you put your foot in it so it should have continuity normally. Look to see if you have power coming and going on the switch/clutch side.
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Senior User
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From: Walterboro, SC
I didn't know the diesel also switched the clutch off at WOT. I'm really sorry you had to look that stuff up. I was looking at diagrams in my Chiltons and it all of a sudden occured to me that I had tested the switch incorrectly. I went back and tested it correctly and the clutch clicked right on!
I let it run for about a minute and the AC never got cool inside. I'm not sure wether the low pressure switch is bad or if the pressure actually is low. Is there any way to check the pressure without buying the recharge kits? I assume you could attach a pressure gauge into the low side hose? What sort of pressure would I be looking for? It seems that 20-25 psi is about right, but I'm not sure.
Thanks alot for your help!
I let it run for about a minute and the AC never got cool inside. I'm not sure wether the low pressure switch is bad or if the pressure actually is low. Is there any way to check the pressure without buying the recharge kits? I assume you could attach a pressure gauge into the low side hose? What sort of pressure would I be looking for? It seems that 20-25 psi is about right, but I'm not sure.
Thanks alot for your help!