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

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis 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 (Diesel Engine)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan)  or Air Conditioning (A/C) System Performance Test (HP2) 
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:
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:
Do the listed conditions exist ?		 Go to Step 5  Go to Air Conditioning (A/C) System Performance Test (Diesel Engine)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan)  or Air Conditioning (A/C) System Performance Test (HP2) 
5 The A/C system has a low refrigerant charge.
Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2)  or Refrigerant Recovery and Recharging (HP2) .
Is the procedure complete?		 Go to Step 6  -
6
  1. Record the low and the high side pressures as well as the instrument panel (I/P) air outlet temperature after you perform the repairs.
  2. 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 (Diesel Engine)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/ Electric Cooling Fan)  or Air Conditioning (A/C) System Performance Test (Gas Engine w/Engine Driven Fan)  or Air Conditioning (A/C) System Performance Test (HP2) .
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
  1. 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 (LMM)  or Discharge Hose Replacement (LY2, LMF, L76 and L92) .
  2. 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
  1. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement (LLY/LMM)  or Air Conditioning Compressor Replacement (LU3)  or Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG)  or Air Conditioning Compressor Replacement (HP2) .
  2. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement .
  3. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2)  or Refrigerant Recovery and Recharging (HP2) .
Is the repair complete?		 Go to Step 13  -
11
  1. Flush the A/C system. Refer to Flushing (Non HP2)  or Flushing (HP2) .
  2. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement .
  3. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement (LLY/LMM)  or Air Conditioning Compressor Replacement (LU3)  or Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG)  or Air Conditioning Compressor Replacement (HP2) .
  4. Replace the accumulator. Refer to Air Conditioning Accumulator Replacement (Non-HP2) .
  5. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2)  or Refrigerant Recovery and Recharging (HP2) .
Is the repair complete?		 Go to Step 13  -
12
  1. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement (LLY/LMM)  or Air Conditioning Compressor Replacement (LU3)  or Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG)  or Air Conditioning Compressor Replacement (HP2) .
  2. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2)  or Refrigerant Recovery and Recharging (HP2) .
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
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