A/C Pressure Switch
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A/C Pressure Switch
Got a 2002 F-250 and the A/C compressor cycles constantly, even after initial startup. Cab does not get cool. Pressure seems ok. Put jumper on pressure switch installed on receiver and compressor stopped cycling. Do I have evacuate the refrigerant to replace the switch?
More Turbo
Joined: Aug 2006
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From: W. Wisc
By what you describe, you are probably low on freon. If so, you have a leak. Find and fix the leak, then recharge the system. But that is not always the issue...
When you say the "pressure seems ok" what exactly does that mean? Do you have a real set of AC gages? If so, what did they read? That is the key to diagnosing this.
This is classic signs of undercharged system, in general, but it can also be the compressor going bad. You need gages to figure it out. No other way. Autozone may rent/loan them, if you have one in the area. If not, they are less than $100 to buy. Not bad to have for a lifetime....
Hook them up with the car off for a couple minutes so the system pressure is down. Same for unhooking them, but wrap a cloth or towel around the fittings so any tracer dye in the system does not spew everywhere.
Ignore the switch for now. You just faked it out by jumpering it. Get gages on it!
-Dave
When you say the "pressure seems ok" what exactly does that mean? Do you have a real set of AC gages? If so, what did they read? That is the key to diagnosing this.
This is classic signs of undercharged system, in general, but it can also be the compressor going bad. You need gages to figure it out. No other way. Autozone may rent/loan them, if you have one in the area. If not, they are less than $100 to buy. Not bad to have for a lifetime....
Hook them up with the car off for a couple minutes so the system pressure is down. Same for unhooking them, but wrap a cloth or towel around the fittings so any tracer dye in the system does not spew everywhere.
Ignore the switch for now. You just faked it out by jumpering it. Get gages on it!
-Dave
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Added bottle of refrigerant and checked pressure which was in the correct range. After full bottle the compressor still cycled. It would only be on for a couple of seconds and off for a couple of seconds.
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From: Georgia
Ambient temp Low side psi High side psi
85* 45-55* 225-250*
90* 45-55* 250-270*
95* 50-55* 275-300*
100* 50-55* 315-325*
Using the chart and checking with a good set of gages (not the el cheapo), :
1) If low side is low and high side is low- add 1 can.
2) If low side is low and high side is high-usually blockage in the system like expansion valve or orafice tube.
3) If low side is high and high side is low-usually faulty valve in compressor (gages usually go nuts when this happens)
4) If low side is high and high side is high-overcharged system also resulting in a not so cold a/c. hope this helps your diagnosis.
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