Ok guys, I have a 99 Sub 4x4 5.7 2500 w/rear a/c. The A/C blows cool but not Cold. I am going to get a thermometer today and check out what temp is comming from the vents. The problem I am having is the A/C compressor clutch engages but wont disengage. The system has roughly 2 pounds of freon in it I know it needs a little more but am afraid ill hurt something with the clutch not disengaging like it should. I am thinking that its the cycling switch on the Dryer but am uncertain and want a second opinion. I live in southern Arizona and during the day its about 100 degrees right now and climbing every day. I am not running the A./C over fear im goint to hurt something. when i got the Sub the A/C worked fine I drained all Freon in it last year to try to get it to cycle again filled it back up with freon and let it be. The system hasent been opened up so it shouldnt need to be evacuated unless someone suspects too much oil in the system. I have access to good guages if I need them. Ive been searching for answers to this Q for an hour in the forums to no avail so any help is much appreciated. thank you

 

Update, took a 10 mile trip to test temp. Ambient was 74 degrees and vent temp was 59 degrees. I know something is definatly wrong other people are recording temps of 39 and 40 degrees. The compressor isnt making any noise and the clutch turns like it should, kind of stiff but not stuck to where you have to put a wrench on it to get it to turn. I am a backyard mechanic but used to work for an auto shop so i am highly mechanicly inclined ive just never dealt with A/C before.

 

Are you saying the clutch will not disengage when electrical power is removed?

In order to provide answers, we need to know temps (both ambient and vents) and hi/lo pressures.

If the compressor clutch isn't stuck to the pulley then it sounds like a low charge but need pressures.

 

Pressure would definitely help us help you. The switch on the drier is the low pressure switch. I would suspect the high pressure switch is the problem. It is the switch in the back of the compressor.

 

If I turn the A/C off then the clutch will disengage. The compressor will not cycle like its suposed to. you know on off on off every so often. Ill get guages today and give hi low readings when i can thanks for the quick reply. Would a half pound of freon be enough to make it not cycle?

 

when it is on max a/c it is not suppose to disengage if the right amount of freon is in there. I think max a/c is when the air recycle is on. most a/c is to be around 30 degrees under outside temp.

 

Low charge would make it cycle faster (short cycle)

 

I have guages but not a pro at using them. Do I take readings at Idle or at a certin RPM. and what pressures do I need to be looking for.

 

ok temp outside was 102 degrees guages read Static low was 80 psi and high was 65 psi when running at idle high was 225 low was 65. at 2000 rpm high was 225 and low was 45. vent at idle was 72 degrees and at 200 rpm it was 62 degrees it only has about 2.5 pounds of freon and it calls for 3.5 lbs. with those readings should i fill it up the rest of the way or is there something wrong with the compressor that im not seeing i do not want to waste the freon if i dont need to Thank you again for the advice. Oh and one more thing the low pressure line and acumulator were cool to the touch not ice cold like they should be.

 

ok put the third 18 Oz can in which is 3 lbs 6 Oz and its working great except the fact that the compressor is not cycling weither at idle 2000 rpm Max A/C or at high withought the recirc on. Im a little stumped about why its not cycling. is it the cycling switch and if it is ill be out 100 bucks for freon and another 80 for the switch.
Also Temp outdise went up to 103 and vent temp was at 52 degrees on low fan setting on high it went up to 58 degrees.