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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1550 (Heating, Ventilation, And Air Conditioning) >> Diagnostic Information and Procedures >> Air Conditioning (A/C) Diagnostics - Pressure Zone C

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

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 and the high side pressures are both higher than normal.
  • Restricted Condenser Air Flow
  • Cooling Fan Malfunction
  • Expansion Device Malfunction
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
  1. With the engine idling, turn ON the A/C.
  2. Inspect for proper cooling fan operation. Refer to Cooling System Description and Operation .
Are the cooling fans ON and operating properly?		 Go to Step 3  Go to Step 5 
3 Visually inspect for the following:
  • Restricted air flow.
  • Damaged condenser cooling fins.
  • Inspect for missing or misaligned air baffles.

Do the following conditions exist?		 Go to Step 4  Go to Step 6 
4 Repair the air flow restriction.
Is the repair complete?		 Go to Step 9  -
5 Repair the cooling fan operation fault. Refer to Fan Clutch Diagnosis .
Is the repair complete?		 Go to Step 9  -
6
WARNING: Refer to Moving Parts and Hot Surfaces Warning .
Feel the liquid line on both sides of the expansion device.Is the temperature the same before and after the expansion device?		 Go to Step 7  Go to Step 8 
7 Replace the damaged/faulty orifice tube. Refer to Expansion (Orifice) Tube Replacement .
Is the repair complete?		 Go to Step 9  -
8 Air is in the refrigerant system, or the system is overcharged. Refer to the view screen on the J 43600  ACR 2000 Refrigerant Station for foreign gas content in the refrigerant. See Special Tools .
Recover 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 9  -
9
  1. Record the low and high side pressures and the I/P outlet air temperature after repairs are performed.
  2. Compare the pressures and 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?		 Go to Step 10  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) 
10 Operate the system in order to verify the repair.
Did you find and correct the condition?		 System OK Go to Symptoms - HVAC Systems - Manual
or
Go to Symptoms - HVAC Systems - Automatic
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