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2002 Yukon-Front Warm-Rear Cool

andyjr on Tue June 17, 2008 9:11 PM User is offline

Year: 2002
Make: GMC
Model: Yukon
Engine Size: 8.1
Refrigerant Type: R134
Ambient Temp: 85
Pressure Low: 28
Pressure High: 160
Country of Origin: United States

My 2002 Yukon AC has started to blow warm through the front, but blows cold from the rear. If only the front AC is on, the compressor clutch cycles on and off as the low side pressure drops to 20psi, which I believe is the low pressure cutout. If the rear AC is turned on, the clutch remains engaged and the low side pressure is steady at 28-30psi and the high side is 150-160, with the engine idling. I am connected to the ports on the line that goes to the front evaporator. Are there other ports, as these are on the same line, separated, I assume, by the orifice tube? I'm a bit puzzled by the pressure drop with only the front AC engaged, but not with the rear AC engaged. Also, the front AC still will not blow cold, even if the clutch remains engaged. This truck has the automatic temperature control system. I have not scanned the ECM, to see if there are any codes present. Any suggestions. Thanks.

mk378 on Tue June 17, 2008 9:51 PM User is offline

Feel the line leaving the front evaporator (returning to the compressor.) If it's good and cold the evaporator is also cold, but the air is being reheated on the way to the vents.

Chick on Tue June 17, 2008 9:55 PM User is offlineView users profile

I suspect a low charge, have the system evacuated and recharged, If cooling returns, find and fix your leak..Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

andyjr on Wed June 18, 2008 5:36 PM User is offline

The return line is warm. Still puzzled as to why the pressures stay up when the rear AC is turned on. I'll have to look at it again. Thanks for the reply. Andy

TRB on Thu June 19, 2008 11:21 AM User is offlineView users profile

Compressor Type
Sierra & Silverado Harrison HU6 6-Cyl
Avalanche, Escalade, Suburban, Tahoe & Yukon With Front A/C
Nippondenso 10S17
Avalanche, Escalade, Suburban, Tahoe & Yukon With Front & Rear
Nippondenso 10S20

System Oil Capacity
Total (Front A/C Only) 8 ozs.
Total (Front & Rear A/C) 11 ozs.
Refrigerant (R-134a) Capacity
Front A/C Only 28 ozs.
Front & Rear A/C (Utility) 42 ozs.
Front & Rear A/C (Suburban) 49 ozs.

System Operating Pressures
High Side 120-171 psi (8.44-12.02 kg/cm2 )
Low Side 26-38 psi (1.83-2.67kg/cm2 )

Specification is with ambient temperature at 80°F (27°C), relative humidity is between 35-60
percent and engine speed at 1500 RPM.


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