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

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

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 appropriate A/C system performance test? Go to Step 2  Go to Air Conditioning (A/C) System Performance Test (Short Wheel Base) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 1500) , Air Conditioning (A/C) System Performance Test (HP2) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 2500) 
2 After continued operation of the air conditioning (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 appropriate 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 appropriate 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 (Short Wheel Base) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 1500) , Air Conditioning (A/C) System Performance Test (HP2) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 2500) 
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) , 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 (Short Wheel Base) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 1500) , Air Conditioning (A/C) System Performance Test (HP2) , Air Conditioning (A/C) System Performance Test (Long Wheel Base 2500) .
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 (W/O C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69) , Expansion (Orifice) Tube Replacement (W/O C69) .
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 (W/C69) , Suction Hose Replacement (W/O C69-HP2) , Suction Hose Replacement (W/O C69) , Suction Hose Replacement (W/C69-HP2) , and to Discharge Hose Replacement (LY2, LMF, L76 and L92) , Discharge Hose Replacement (HP2) .
  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 (HP2) , Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92, LC9 and LMG) .
  2. Install an A/C refrigerant filter. Refer to Air Conditioning (AC) Refrigerant Filter Replacement (C69) , Air Conditioning (AC) Refrigerant Filter Replacement (C69-HP2) .
  3. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement (W/O C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69) , Expansion (Orifice) Tube Replacement (W/O C69) .
  4. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2) , 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) , Flushing (HP2) .
  2. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement (W/O C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69-HP2) , Expansion (Orifice) Tube Replacement (W/C69) , Expansion (Orifice) Tube Replacement (W/O C69) .
  3. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement (HP2) , Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92, LC9 and LMG) .
  4. Replace the accumulator. Refer to Air Conditioning Accumulator Replacement (HP2) , Air Conditioning Accumulator Replacement (Non-HP2) .
  5. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2) , 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 (HP2) , Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92, LC9 and LMG) .
  2. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging (Non-HP2) , 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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