2002 GMC Sonoma Air Conditioning Issues - Truck Trend Garage - TruckTrend Magazine
Q: The A/C won't work on the 2002 GMC Sonoma I just bought. I charged the system with R134a from the parts store going by the instructions, it seems to hold refrigerant, and I don't see any visible leaks. The compressor and clutch both turn freely, but when the compressor engages, it clicks on for a couple seconds and then clicks off. Assuming the charge is correct, here are a couple of possible causes going by your description: It could be that an electrical problem is not keeping the A/C compressor clutch engaged. There might be an internal system obstruction affecting system pressures. For example, A/C systems have low pressure and high pressure service ports where you hook up the gauges. Normal operation should be around 150 psi on the high side and 25 psi on the low side. The expansion valve at the evaporator is what varies the pressure drop of the system. When this valve gets stuck in the closed position, the low side goes very low (even a vacuum) and high side pressure shoots way up. This can produce your symptoms. As soon as the compressor engages, the system pressure switch sees the low side pressure drop to nothing, and disengages the clutch immediately. After high and low side pressures equalize, it will repeat the cycle. Source: www.trucktrend.com
