2001 gmc yukon 1500

[kenstire67]

this truck has been at 2 shops now ours, ac blows 80 deg, we replaced all hoses and lines, evaporator, condenser, dryer, orfice tube, expansion valve, compressor, flushed all, added oil and vacuum for 30 min, charged 2.8 lbs. at 1800 rpm blows 60deg air high side is 250 and low side 45 , at idle high side is 275 sometimes 300 and low side is 70 to 79 , I checked with a help desk at gm and the guy went thru the water the condenser and yes pressure goes down, the fan clutch is working and spinning the correct direction , he says the compressor is the issue. im not sold on compressor this is the 3rd compressor im going to put on and the pressures have stayed the same. if anyone has an idea I would greatly like the help.when everything is new its a mind blower , and the parts are from gm dealer, thank you for any help and I would greatly repay the favor to help some one else.

[bohica2xo]

Fan clutches get tired. they still spin, just not very hard.

Put a helper in the driver's seat, feed the gauge lines through the passenger window & watch them. Drive the truck 45 to 50 mph - the air speed where the fan does very little work.

Here is some more info on testing clutches:
https://www.autoacforum.com/messageview ... adid=10772

[GM Tech]

On trucks with issues after parts have been replaced, I always look for 2 orifice tubes in system- most all condensers have an OT in their outlet connection- yet rear air systems have their OT at the split (to rear) in the liquid line outlet--- so If you bought a new condenser- chances are real good there was an OT in it, and you also have one in your split connection- which will drive you crazy in trying to diagnose poor cooling....

[Cusser]

Fan clutches get tired. they still spin, just not very hard.

When I read the original post this morning, I also was thinking fan clutch. Just last month I replaced the fan clutch in my 1988 Mazda truck - again. These seem to last about 6 years here in Phoenix.

[bohica2xo]

Yep. Spray water on new condenser, pressure drops. Either defective partially blocked condenser or lack of airflow. Since all of the testing is being done in the work bay...

GM Tech does have a point about finding two orifice tubes. Good idea to check for that as well.