AC pressure very high, need help!
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From: Oak Ridge, TN
AC pressure very high, need help!
Alright, my 99 F250 air conditioning is giving me some trouble. Over the past few months, it has slowing been getting warmer and warmer air into the cab. It will cool decently when it is first started up in the morning, but after another start up, it doesn't blow cold air. I checked the pressure on the condenser (big can lookin thing). There was a fitting there, so I checked it there, and the psi said 150, no ****, just a few minutes after I shut it off. Then I tried it with the motor running and AC going, and it said about 130. Is there somewhere else that i'm supposed to check it? I really like my cold air, so any suggestions are welcomed. Thanks.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
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From: Lorain County, Ohio
You are measuring the static system pressure. 130-150 is not excessive on a hot day with a warm engine. You're going to need more than that little low side gauge to diagnose your problem.
Does the compressor run when you turn on the AC?
Does the compressor clutch cycle on and off with the AC on? How often?
Is the clutch engaged when the cooling stops?
This sounds like a clutch gap issue, but post back with answers to those questions.
Does the compressor run when you turn on the AC?
Does the compressor clutch cycle on and off with the AC on? How often?
Is the clutch engaged when the cooling stops?
This sounds like a clutch gap issue, but post back with answers to those questions.
Last edited by lsrx101; Jun 30, 2007 at 10:25 PM.
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Freshman User
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From: Oak Ridge, TN
No, the compressor isn't engaging. So I guess i'm gonna have to replace it. However, that still doesn't explain the really high pressure, 100+ psi and both low and high side. There may be a plugged orfice or something, I'm not sure. Any other thoughts on this???
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
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From: Lorain County, Ohio
The compressor is probably ok, it's just not engaging Tthat pressure is normal with the compressor not running. The system is equalized.
Find the Low Side Cycling Switch on the accumulator (the big metal can looking thing) Pull the connector and jumper across the connector terminals. Does the compressor engage? (engine running, AC on) If so, replace the cycling switch. That switch should close at 42psi.
If not, reconnect it and and carefully tap the face of the compressor clutch with a broomstick. Does it engage then? If so, adjust the compressor clutch gap.
If not, you'll need to do some electrical testing.
Find the Low Side Cycling Switch on the accumulator (the big metal can looking thing) Pull the connector and jumper across the connector terminals. Does the compressor engage? (engine running, AC on) If so, replace the cycling switch. That switch should close at 42psi.
If not, reconnect it and and carefully tap the face of the compressor clutch with a broomstick. Does it engage then? If so, adjust the compressor clutch gap.
If not, you'll need to do some electrical testing.
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From: Oak Ridge, TN
Alright, I pulled the switch off and jumped it...nothing, compressor still wouldn't kick on. So I took broom handle and knocked the clutch, boom, it engaged. I let it run a minute, turned the ac off, and turned it back on, and it engaged. So hopefully it will work for a while. I got a date with a mechanic on thurs to fix it. I guess i'll see how it goes for the next couple days. One thing though, if i leave the ac on when i turn the truck off, the clutch will still be engaged when i turn it back on, so the ac should work...i would think. Thanks for the help.
Fleet Mechanic
Joined: Feb 2006
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From: Lorain County, Ohio
Originally Posted by cobramustangboy
Alright, I pulled the switch off and jumped it...nothing, compressor still wouldn't kick on. So I took broom handle and knocked the clutch, boom, it engaged. I let it run a minute, turned the ac off, and turned it back on, and it engaged. So hopefully it will work for a while. I got a date with a mechanic on thurs to fix it. I guess i'll see how it goes for the next couple days. One thing though, if i leave the ac on when i turn the truck off, the clutch will still be engaged when i turn it back on, so the ac should work...i would think. Thanks for the help.
The compressor clutch gap is too wide. Remove the clutch center bolt and pull the clutch hub off. Remove a shim from the hole where the compressor shaft indexes (it may fall out when you remove the plate, be careful). Reinstall the hub, you should be good to go. It takes 5 minutes.
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From: Oak Ridge, TN
Alright, I will try that tomorrow and see if it works. So I just need to take the center bolt off. Is anything under compression...will anything fall out when I take the hub out, I don't know enough about compressors and ac to go tearing through components. Thanks.
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Fleet Mechanic
Joined: Feb 2006
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From: Lorain County, Ohio
Originally Posted by cobramustangboy
Alright, I will try that tomorrow and see if it works. So I just need to take the center bolt off. Is anything under compression...will anything fall out when I take the hub out, I don't know enough about compressors and ac to go tearing through components. Thanks.
Use a pair of channel locks across the pulley to hold the clutch plate. Remove the bolt, slide the plate off. Watch in case the shims fall, they usually don't though. The shim(s) are in the hole that slides onto the compressor shaft. It will become obvious when you see it. If there's only one, remove it. If more than one, remove one. Slip the clutch hub back on, install the bolt. Make sure you get it tight. Check to make sure the plate doesn't rub the pulley when you spin it. I'd be surprised if it takes more than 10 minutes. Probably more like 5.
You might need a couple of screwdrivers to persuade the plate to come off if it's a little sticky. You usually don't.
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Thread Starter
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Freshman User
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From: Oak Ridge, TN
Well ****, I pulled the hub off, there were no shims to be found. So I put it back on, and my buddy that was helping me over torqued the bolt and sheared the head off, leaving the rest off the bolt screwed in, and there isn't enough left out to grab onto, so now i'm stuck. It looked like it may have to be drilled out. Any suggestions very welcomed.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
Originally Posted by cobramustangboy
Well ****, I pulled the hub off, there were no shims to be found. So I put it back on, and my buddy that was helping me over torqued the bolt and sheared the head off, leaving the rest off the bolt screwed in, and there isn't enough left out to grab onto, so now i'm stuck. It looked like it may have to be drilled out. Any suggestions very welcomed.
