AC cuts out over 1k RPM - Ford Powerstroke Diesel Forum
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Old 06-07-2013, 09:52 AM
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AC cuts out over 1k RPM

I have an 03 250 6.0L that the ac works fine until a good heat soak and then the compressor shuts off at 1000 rpms and above. The PCM is showing a WOT shut off condition. The APPS is not setting any codes and the values are within Ford specs, no spikes or dips in voltage throughout the pedal sweep. APPS % shows 0 @ idle and 99.5 @ WOT and is smooth between. I am thinking the PCM is faulty but was wondering if anyone has run across this before? Does the PCM have any other means of determining WOT? Thanks in advance
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Old 06-07-2013, 11:29 AM
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Ive seen where ac compressors will do similar if there isnt enough oil due to old/ loss of freon. Have you checked the charge in your AC? Could also be a weak compressor clutch as a guess. Im not too savvy with the ac system but those are some ideas to start I guess.
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Old 06-07-2013, 11:48 AM
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The AC has the proper charge and the pressures are spot on. The clutch drive plate air gap is re set to 0.016. The AC works great until after a heat soak then the PCM shuts down the AC relay under a WOT condition. I just don't want to throw a $700.00 part at ti until I am sure that's it.
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Old 06-07-2013, 12:00 PM
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thats it...plain and simple. I dont feel like explainging
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Old 06-07-2013, 12:31 PM
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I know that it will shut it down under the wot condition but the PCM is doing that at any rpm over 1k, it's not normal for it to do that.
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Old 06-09-2013, 10:49 AM
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What's your fan doing? My buddies truck did the same thing I went thru the entire ac system still did it, his fan clutch was not engaging to pull air thru everything. Instead of spending 300 on a clutch I spent $60 on 2 12 inch fans and $35 on a thermostatic relay to turn the fans on when the ac is turned on. Mount em to the front of the condenser and hook up the relay, don't worry about making the relay come on other than when you turn on the ac. Can't remember which wire is the positive to engage the ac clutch but its nit hard to figure out. Cheaper fix than $300 fan clutch and a couple hours of work trying to get the thing off
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Old 06-09-2013, 11:44 AM
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Didn't explain why, my bad. There isn't enough air being pulled through the condenser. That's why I asked about the fan clutch, if it isn't pulling air through to cool off the hot freon it's not going to bring the pressure down enough to keep circulating, normal pressures are 40-50 low side and generally around 250 high side. Can fluctuate depending on ambient air temps. Without enough air going thru the condenser it won't let the ac system work properly, easiest test to do to find out if your getting enough air being pulled thru is stick a dollar bill to the condenser if it stays there your fine. If it don't stick you don't have enough. Have someone rev the motor to 1500 rpm an I'd imagine it'll cut off and try. Betcha it don't stay. Cheapest fix than a new clutch and antifreeze and the headache of getting the fan clutch to break loose from the pulley.
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Old 06-09-2013, 01:38 PM
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^ I want to add some more detail to this. If the condenser is clogged and not moving enough air thru it- your "head pressure" high side, will spike up in pressure and cut out on "high head pressure".. These trucks I don't think have a high pressure switch, they only have a low pressure switch or "loss of pressure" switch. Its either a clutch- most likely, or the condenser is clogged causing the compressor to trip out on internal overload from the high head pressures... Clean the condenser coil and start from there. Use a non acid coil cleaner. Simple green will not work.
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Old 06-09-2013, 01:42 PM
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Yes it does have a high side pressure switch, it's located really close to the compressor, booger to change when it won't come loose.
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Old 06-09-2013, 05:16 PM
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Ok. Well then- the compressor could be tripping on high head pressure. Need to put gauges on it to verify.
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