what would make a/c work intermittently - Ford Powerstroke Diesel Forum
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Old 08-20-2011, 06:18 PM
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what would make a/c work intermittently

took it to the shop and at the time it wouldnt work at all then they replaced a relay now it works for bout 3-5 mins then stops for 1-2 mins then starts cooling again then it stops again for a few mins ?? also. i know on gasers the a/c will hurt mileage is diesels the same ?
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Old 08-20-2011, 07:57 PM
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Generally speaking, AC systems will have a pressure sensor that protects it and stops it from running in an ‘under-pressure’ situation. If it wasn’t checked already, have the system pressure and refrigerant charge tested. For instance, you could have a tiny leak in the system that finally let the system pressure down to a value just below where the sensor cuts off the compressor so it doesn’t hurt itself. If your AC has gotten warmer and warmer, and then finally stopped working, this could be a likely scenario for you and easy to temporarily fix – then you have to figure out where the leak is and fix it. Whoever checks your system should have a manual to tell them what the proper pressure should be – I don’t know what it is. It would be interesting to find out, though.

Other possibilities are (however likely or unlikely): is a failed or intermittent system pressure switch (high or low cutout); dirty compressor clutch electrical connector; iced or dirty evaporator; refrigerant overcharge condition; faulty compressor; block in the system. Something else might be possible, these are just malfunctions that come to mind.

I hope someone chimes in that can identify the most commonly seen AC failure in our trucks to help you narrow it down. Best of luck and I hope you find the problem soon.
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Old 08-20-2011, 08:48 PM
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whell the pressure was checked when they found the relay. it was like 105 psi and i can check it but as soon as i left the shop it started . and ive noticed i dnt think it is as cold as it should be for a bigger truck. but i have nuttin to compare it too tho.with this being the first f350 ive ever owned
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Old 08-21-2011, 07:34 AM
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I just had the same problem with my truck. The compressor I had was coming apart internally, and was actually overpressuring the system, causing a cut out, until the pressure came back down, then it restarted. Lather rinse repeat.

Replaced the compressor, drier, and all related components. It now blows snow out of the vents... well, almost.
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Old 08-21-2011, 09:00 AM
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wow i was hoping i wouldnt have to replace all that but owhell do what i gotta do to make wife happy.lol i dont use a/c but she cnt live without it
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Old 08-21-2011, 09:36 AM
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Well, it's been over 100 down here for 20 days in a row now with absolutely no rain for the past month and a half. I gotta have cold AC, no expense spared!

Also, the load on the system of an AC compressor is sooooo small overall compared to everything else, you're not really going to see a gas mileage impact. Driving around, windows down, will actually lower your mileage more than using AC, as the windows being down affects the aerodynamics of the vehicle, causing more wind drag.

Last edited by Dicion; 08-21-2011 at 09:40 AM.
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Old 08-21-2011, 10:22 AM
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I watch the mpg's very closely. IMO there is at least a 1 mpg impact due to having the A/C on.

Last edited by bismic; 08-21-2011 at 12:59 PM.
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Old 08-21-2011, 06:06 PM
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ok whell its only in the 90's here in nc . but i try to run just the fan with the windows cracked. but sometimes the a/c needs to b run. and that was what i was thinking as much torque it has i didnt think it would hurt the gas mileage but r they any way to test the parts? on the a/c ? i cnt hear anything grinding or no bearings wearing out ??
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