AC Question

[Egg_Head]

I have a 2011 GMC Acadia with intermittent AC issues of blowing cool, cold & warm. I purchased a set of gauges and got the following readings at about 60 degrees F. Low side was 10 psi, High side was 150 psi at start up, after 5 minutes of idling numbers came up to 17 psi Low and 175 High. Based upon provided chart High side seems to be above the range of 135-155 psi and Low side should be between 25-35 psi. My question is: Based upon the numbers provided, what is the system diagnosis?

 

[Chris142]

Have a shop suck it out and see how much was in it. Only way to do r134a correctly. Plus 60 degrees is too cool for a proper diagnosis.

Make sure your cooling fan is working correctly.

 

[mehullica]

60 degree ambient temp is still warm enough to get a good gauge reading. Your low side is too low, high side is a little high. You have a restricted low side issue. Not sure what device the GMC uses to meter flow through the evaporator. Expansion valve or orfice tube type. Your issue is going to be a failed part or debris from the compressor or hoses restricting the expansion valve/orfice tube

 

[mk378]

If it is intermittently working, you have to test it when it is not working.

Common reasons for sometimes blowing cold and sometimes warm would be the compressor clutch not always engaging, or the expansion valve sticking closed. In case of a stuck expansion valve you will find the compressor turning, but a very low low side pressure and air not cold.

The high side doesn't tell much on cars with electric fans because the fans are controlled by pressure, which will let the high side rise (even with low charge of refrigerant, etc) until the fans start.

 

[WobblyElvis]

At 60F before operation the pressure should be much greater than 10psi. I would ad a small amount of r134a and I think you have a leak.