Hi, i own a 92 f150 5.0 and have been having issues with my AC, i have replaced my low pressure cycling switch, my compressor, i oiled the system and refilled it with refrigerant, i inspected all my lines and they look good, but everytime i turn my ac on the compressor will cycle on and off every 3 seconds, and my ac will blow hot and very rarely cold for a second or two. Any idea what could be going on?

 

Clogged orifice tube or dryer/receiver possibly.

 

It's still not all the way full of freon is my guess
You had a gauge set on there while it was cycling fast?
Neds to be around 30psi on the low side
Roughly
Above 24 will turn on the compressor
Below 24 will turn it off
There are cycle time / pressure relationship charts in the book
Generally, fast cycle time means low freon level

 

I will hook the gauges back up and double check, and is there a way for me to check that tube without having to drain the lines?

 

Moderately competent shadetree mechanic advice offered here, FWIW - low on freon will generally show low pressures on both the high and low sides. A plugged orifice will typically show high pressure on the high side, low pressure on the low side. Know of no way to inspect the orifice / dryer without draining the system.

IMO, what qualifies as high and low pressures on either side relates to experience with my '89 R12 unit, where I'd generally look for 250-275 on the high-pressure side, and 30-40 on the low-pressure side. The system is supposed to be filled by weight given on the sticker, as actual observed pressures will vary due to ambient temperatures, blower fan speeds, and the like. IIRC, when checking pressures, the blower fan should be on Hi.

Offering that it was normal for the compressor to cycle in moderate ambient temperatures and/or low blower fan speeds, however this 'normal' cycling was more towards the 10-15 second interval.

 

No, the freon needs to be removed to remove and inspect the orifice tube
Yours is stuck into the high side evaporator line at the evaporator
I use hemostats to pull them out

 

Agreed, found it a real PITA to pull, especially if clogged and otherwise crudded up. On the other hand, the degree of difficulty corresponded to likelihood of finding and fixing the right problem.

 

Thank you guys for all the help, will be draining it shortley to pull the tube, will check it, clean it, or replace it depending on how bad it is.

 

What makes you think the orifice is plugged or needs inspected?
Put a gauge set on the vehicle and check the pressures
Unless the low side is extremely low (0-10 lbs.) and the high side higher than normal (250-300 lbs.), the orifice is not plugged

 

Ok i will hook the gauges up to it today