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AC hot, then cold, then hot etc.

Shawnee on Wed June 17, 2015 9:35 PM User is offline

Year: 2008
Make: MB
Model: C300
Engine Size: V6
Refrigerant Type: R134a

Wife complained last night AC was not working. Got in the car this morning and seemed to be working fine. Checked the low side pressure and seemed fine (can't remember the pressure but think it was around 25 or so). Got in the car this evening and no AC. will be cool for a second or so then hot Checked pressures Low-70 Hi-160 Amb temp - 85. Turned the car off and went inside to check the web for pressures reading at thoughts. Went back out five minutes later and started the car up and AC blowing cold now. Had already returned my manifold set so check the low side with a gauge I had and it was about 30 now. Any ideas as to what might be happening. My wife is not happy so need help desperately!!!!! Thanks for your help and ideas.

GM Tech on Wed June 17, 2015 9:38 PM User is offline

Is the front of compressor turning when a/c goes hot???? stop and pop hood sometime...

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Shawnee on Wed June 17, 2015 9:55 PM User is offline

Will check the next time. Still working fine now. Problem just seemed to start when we started getting temps close to 100 degrees the last couple days here in NC. Did notice earlier that the aux fan was hauling butt when it was not working. Temp is lower now so the fan is not working as hard now. just some general observations.

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