My 2007 F-250 6.0L diesel A/C freezes you out of the cab when you turn it on with a cold start. It will continue to do this as long as you drive it. However, after a hot soak, when you turn the A/C on, the compressor turns off and on much quicker than normal, and cooling is very weak. Over about 5 minutes, it gets better, but usually doesn't get really cold, just comfortable with the blower on '3' and max air selected. The you can feel the compressor cycling when you hold your hand by the A/C vent.

My two thoughts are....

1) It's a little low on refrigerant. When I bought the truck I complained about it and they evacuated the system, measured the refrigerant removed and said it had a full charge. They said they recharged it with fresh refrigerant. It was cold out and I didn't get to check it. The problem was still there, but the place I bought it from is 225 miles from here. I went out and planned on connecting my gauges to the system, but it turns out I don't have an R-134A adapter to connect my gauges. I will look for one today.

2) The A/C cycling switch is going bad. Does Ford use a Shraeder valve on their switches?? If so I could change the switch without evacuating the system.

Any other possibilities??

 

I'd have the cycling pressures checked.
The low/cycling is valved..

 

The adapters I need to connect my gauge set should be here by the end of the week.

 

The adapters arrived and I took some pressure tests. It's about 92 degrees now. The truck was hot, and once the fan was up to speed (it's controlled by the ECU on a diesel) my idle low side pressure was about 35# and the high side was about 180#. With the AC on outside air, the discharge temp probably was about 60 degrees F. If I raised the engine to about 1200 RPM, the compressor would start cycling off when the Low SIde presure got down to about 20#, it'd switch off for about 8 seconds and then turn on at about 55# and then quickly go back down to 20#. By quickly I mean less than 5 seconds of running. The High side stays about 180# when the compressor is running and the engine is going about 1200 RPM. When the engine is idling, the evaporator discharge line is warm, and when the engine is running @ 1200 RPM, it just starts to get cooler.

I looks to me like the system is a little low on refrigerant. At 90 degrees F shouldn't the high side be about 250-270# or so?

 

Add refrigerant.