Yukon A/c Problem

[jesterdog]

I have a 1999 Yukon with 5.7L. Lately the A/C hasn't been cooling very well. With it on max recirculate, it just isn't cutting it. So, I put my little guage on it and it showed 45psi (in the blue zone) which indicates that the freon charge is good. Hmmm...I put my temp probe in the a/c vent and it is only blowing about 72 degrees. I forgot to look at the accumulator can (or is it evaporator?)to see if it was cold and wet. But, it was not puddling water on the ground like normal. However, the rear of the car (near ex pipe) was. So later that day on the way to church, I reach back and feel the rear air. It is ice cold. I haven't put the temp probe to measure it yet. Why would the front and rear air blow 2 different temps? Heater control valve stuck? Fresh air damper stuck. Do those things affect the rear air the same as the front?

 

Thanks for your help!!!!!!!

[atboley]

first of all, is the compressor cycling alot? like only staying on for 5-6 seconds at a time... second of all you need to check pressures running, if your low side drops from 45 to 25 very quickly as soon as the compressor engages then your low on freon. you also need to chec high side pressures while its running, rev it up and make sure the high side doesnt go any higher than maybe 300 at the very most... there is really no go explanation i could think of that the front would not be cold and the rear would unless you have a plugged evaporator or somthing or if your temp door is stuck but i doubt either of those. so if there is any restrictions in the system it will show up with to high of high side pressures... but those trucks are well know for the compressors leaking and being low on freon, rarely is there anything else wrong with them besides that...

 

BTW, was thise 45 psi reading you took with the truck off and sitting there? because that is pretty low if the truck had been sittiong for alittle bit, generally the high and low side should be equal the the outside temperature...