Air Conditioning (A/C) Diagnostics - Pressure Zone B

WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Yes	No
DEFINITION: The low side pressure is higher than normal and the high side pressure is lower than normal. Malfunctioning A/C compressor Refrigerant under charge
1	Were you sent here from the A/C System Performance Test?	Go to Step 2	Go to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine)
2	After continued operation of the A/C system, do the low and the high side pressures equalize or become static?	Go to Step 5	Go to Step 3
3	Refer to the pressures recorded during the A/C System Performance Test. Inspect for the following conditions: CAUTION: Refer to Moving Parts and Hot Surfaces Caution . The low side pressure is equal to or greater than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine) . The high side pressure is less than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine) . The low side refrigerant line at the compressor feels cool-to-warm. The high side refrigerant line at the compressor feels warm-to-hot. Do the listed conditions exist?	Go to Step 5	Go to Step 4
4	Refer to the pressures recorded during the A/C System Performance Test. Inspect for the following conditions: CAUTION: Refer to Moving Parts and Hot Surfaces Caution . The low side pressure is greater than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine) . The high side pressure is less than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine) . The low side refrigerant line at the compressor feels warm. The high side refrigerant line at the compressor feels warm-to-hot. Do the listed conditions exist ?	Go to Step 5	Go to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine)
5	The A/C system has a low refrigerant charge. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Is the procedure complete?	Go to Step 6	-
6	Record the low and the high side pressures as well as the instrument panel (I/P) air outlet temperature after you perform the repairs. Compare the pressures and the panel outlet temperature to those listed in the A/C Performance Chart. Refer to Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan) or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan) or Air Conditioning (A/C) System Performance Test (Diesel Engine) . Are the readings within the specified ranges found on the A/C Performance Chart?	Go to Step 13	Go to Step 7
7	The A/C compressor is malfunctioning. Remove the expansion device and inspect for contamination. Refer to Expansion (Orifice) Tube Replacement . Did you find metal flakes on the expansion device?	Go to Step 9	Go to Step 8
8	Inspect the expansion device for a brown, powdery residue indicating desiccant in the A/C system. Is a brown, powdery residue present?	Go to Step 11	Go to Step 12
9	Remove the suction and the discharge lines from the compressor. Refer to Suction Hose Replacement (LY2, LMF, L76 and L92) or Suction Hose Replacement (LMM) and Discharge Hose Replacement (LY2, LMF, L76 and L92) or Discharge Hose Replacement (LMM) . Inspect for metal flake contamination at the line connections and the compressor ports. Is metal flake contamination present?	Go to Step 10	Go to Step 12
10	Replace the A/C compressor. Refer to Compressor Replacement (LLY/LMM) or Compressor Replacement (LU3) or Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG) . Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement . Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Is the repair complete?	Go to Step 13	-
11	Flush the A/C system. Refer to Flushing . Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement . Replace the A/C compressor. Refer to Compressor Replacement (LLY/LMM) or Compressor Replacement (LU3) or Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG) . Replace the accumulator. Refer to Accumulator Replacement . Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Is the repair complete?	Go to Step 13	-
12	Replace the A/C compressor. Refer to Compressor Replacement (LLY/LMM) or Compressor Replacement (LU3) or Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG) . Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Is the repair complete?	Go to Step 13	-
13	Operate the system in order to verify the repair Did you find and correct the condition?	System OK	Go to Symptoms - HVAC Systems - Automatic