AC cycles on and off - Ford Powerstroke Diesel Forum
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Old 06-07-2010, 01:31 PM
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AC cycles on and off

Help its getting hot and I have no ac! I have pleanty of freon. I watch the pressure go up as it cycles on and then no pressure and the air gets hot again. This happens over and over about every 5 seconds. Im not sure where to start.
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Old 06-07-2010, 01:33 PM
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mine does this as well and it seems that my vaccum pump is constantly running under the hood.
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Old 06-07-2010, 01:36 PM
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Do you think its some kind of electrical problem?
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Old 06-07-2010, 01:39 PM
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A/C issues

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oops, i didn't realize this was 6.0 forums. well....... i'd imagine the 6.0 clutch can still go out in a similar way
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Old 06-07-2010, 04:36 PM
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You need to charge the system. The low pressure switch is probably cycling the compressor.
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Old 06-08-2010, 05:15 AM
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i just had the same issue. the compressor was clikcing on and off every 5 seconds or so with no cold air but i had plenty of pressure. I'm not a mechanic but i'll tell you what it was on my truck, (jsut don't break my stones too hard if I use the wrong term for something!!!) Anyway if you feel the lines going in and out of the evaporator, the one refrigerant line goes into the evaporator was ice cold but the other one coming out wasn't cold at all. I guess this is very tell-tale that the evaporator was all clogged up. I had to put in a new evaporator and orifice tube. i had to keep charging and evacuating the system and cleaning out all the grit from the orifice filter rube. I've heard people call that grit "the dessicant" but i'm not sure if that's the right term or not. anyway that fixed it. new evaporator and new orifice tube. the evaporator was about 85 bucks and the new orifice tube was like 4 bucks. Hope that helps.
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Old 06-08-2010, 06:50 AM
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Check the pressure. I got all crazy replacing parts on the AC in my old rig and it just needed proper pressure.

Although, that may indicate that you have an issue somewhere else......start with checking the pressure.

Thad
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Old 06-08-2010, 07:09 AM
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Quote:
Originally Posted by PGreenSVT View Post
You need to charge the system. The low pressure switch is probably cycling the compressor.


Quote:
Originally Posted by johnnyroastbeef View Post
i just had the same issue. the compressor was clikcing on and off every 5 seconds or so with no cold air but i had plenty of pressure. I'm not a mechanic but i'll tell you what it was on my truck, (jsut don't break my stones too hard if I use the wrong term for something!!!) Anyway if you feel the lines going in and out of the evaporator, the one refrigerant line goes into the evaporator was ice cold but the other one coming out wasn't cold at all. I guess this is very tell-tale that the evaporator was all clogged up. I had to put in a new evaporator and orifice tube. i had to keep charging and evacuating the system and cleaning out all the grit from the orifice filter rube. I've heard people call that grit "the dessicant" but i'm not sure if that's the right term or not. anyway that fixed it. new evaporator and new orifice tube. the evaporator was about 85 bucks and the new orifice tube was like 4 bucks. Hope that helps.
That's how its supposed to work. The evaporator is removing heat from the cabin air by absorbing it into the freon . You probably had low pressure, and after replacing the evaporator, you filled the system to capacity



To the OP, if you're checking pressure on the HP side, you're gonna have pressure. Check the suction side, it may start with pressure, because the system pressures have equalized after it shuts down, but as soon as it cycles the compressor, your suction pressure will drop, causing the LP switch to shut the compressor down
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Old 06-08-2010, 03:15 PM
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I checked the pressure and topped it off before I posted. I watched the pressure go up when the system cycled on and then I could watch the pressure release when it cycled off. There is pleanty of pressure in the system. Any other ideas???
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  #10  
Old 06-09-2010, 04:20 AM
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Quote:
Originally Posted by pwrstrkect2009 View Post
I checked the pressure and topped it off before I posted. I watched the pressure go up when the system cycled on and then I could watch the pressure release when it cycled off. There is pleanty of pressure in the system. Any other ideas???
Maybe a bad LP switch, or a weak clutch . Stupid question, is the fan on when you're checking this stuff? I know the switch is on, but maybe the speed selector, or the motor is going bad, and isnt actually on when you're doing your pressure checks. Possibly a dirty evaporator?

Try and jump the LP switch out, and run it with the gauges connected. If it stays running and your pressures are good, then it might be just a bad LP switch. You are checking both the HP and LP sides of the system right?
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