Engine Size: 7.3
Refrigerant Type: 134A
Ambient Temp: 70
Pressure Low: 20
Pressure High: 140
Country of Origin: United States
We had a couple of warmer days and I noticed my A/C was working intermittently. It works at idle, but any rpm up to 2K and it will start cycling on and off every 5-7sec. At 2k it will stay running longer up to 2 min before it cycles as long as the fan is on high and the A/C is set to max. I put my gauge set on it and found the following. The temp was 70 deg. with low humidity and the truck hadn't been run for several hours. All readings were taken with the A/C set to max, the doors closed and the fan on high.
Static Low 87 High 92
Idle Low 35 High 140
On Low 20 High 160 *the compressor cycles on and off every 5 sec
Off Low 40 High 70 *this is the pressure the system returns to before cycling again
If I leave the A/C on max with the fan on high and stay above 2K the compressor will run for 2 min before getting below 20 and cycling off. If I turn the fan down and keep the rpm the same the low press. will drop below 20 quickly and the compressor will start cycling. Any lower rpm and as soon as the compressor kicks in the press drops within a couple of sec below 20. Any help is appreciated
As you will hear from others here, the first thing is to insure that you have the proper charge. Your static pressures listed calculate for a temperature over 100F so maybe the engine, etc. wasn't cooled down yet?
I think you've leaked some refrigerant, from your description and the high side pressures. So you need to find/repair the leak, first step.
Ok, wptski is saying the system is overcharged.......and Cussboy is saying I have a leak and it is undercharged. The vehicle had not been run for several hours and was at ambient temps. I have looked all over for signs of a leak and can't find anything. I hear a hissing sound after shutting down the vehicle around the evaporator/accumulator area. I pulled the cover off the accumulator and it looked fine. The system doesn't appear to be losing any pressure. The pressure are always the same everytime I check it and the hissing sounds stops after a minute or two
Is this the first issue to ever appear in this 11 yr. old truck? If so, it would seem to be the classic symptoms of cycling due to low charge (system is protecting itself). You would need to recover, vacuum, and recharge proper amount of refrigerant by weight and add some dye. If cycling stops and pressures are more normal; you have verified and solved the problem. Then you can start looking for where the dye trace shows and where the leak is at. The leak may be hard to find and the loss would be considered normal due to age. If the cycling returns fairly quickly, you have a gross leak that will need to be found and fixed. HTH
If the air conditioner compressor is turning on and off rapidly , then you do not have to replace compressor. The compressor is the heart of the a/c. You just need to recharge it and that should solve the problem.
heating and air conditioning repair
Aircon Expert - Aircon
Edited: Sat May 02, 2015 at 10:00 PM by deshawn1777
Fords at that time had bad cycling switches. Just something else to check.
Edited: Sun May 03, 2015 at 5:52 AM by Dougflas
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