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

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Value	Yes	No
DEFINITION: The high and low side pressures may be normal or slightly less than normal. Air Delivery Concern Slight Refrigerant Under Charge Refrigerant Contamination
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 (without PHT) Air Conditioning (A/C) System Performance Test (with PHT)
2	Refer to the panel air outlet temperatures recorded during the A/C system performance test. Does the discharge air temperature between the right and left center panel outlets vary by more than 1-2°C (2-3°F)?	-	Go to Step 7	Go to Step 3
3	Did the customer mention that the A/C system output temperatures are good at first, but then turn warm during extended drives?	-	Go to Step 4	Go to Step 5
4	Increase engine speed to 2000 RPM. During extended operation of the A/C system, does the low side pressure decrease, possibly accompanied by heavy frost on the liquid line between the expansion device and the evaporator?	-	Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D	Go to Step 5
5	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 in Cautions and Notices. The high side pressure is slightly greater than the specified pressure ranges but still within Zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to Air Conditioning (A/C) System Performance Test (without PHT) Air Conditioning (A/C) System Performance Test (with PHT) . The discharge line is hot. The suction line is cool. Do the listed conditions exist?	-	Go to Step 7	Go to Step 6
6	Refer to the pressures recorded during the A/C system performance test. Inspect for the following conditions: The low side pressure is slightly lower than the specified pressure ranges but still within Zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to Air Conditioning (A/C) System Performance Test (without PHT) Air Conditioning (A/C) System Performance Test (with PHT) . The discharge line is warm-to-hot. The suction line is cool-to-warm. Do the listed conditions exist?	-	Go to Step 8	Go to Too Hot in Vehicle in HVAC Systems- Manual or Too Hot in Vehicle in HVAC Systems - Automatic
7	The A/C system may be undercharged. Leak test A/C system. Refer to Leak Testing . Recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging . Is the action complete?	-	Go to Step 14	-
8	The A/C system may be contaminated. View the information screen on J 43600 ACS 2000 Air Conditioning Service Center for detection of foreign gases in the A/C system. Do foreign gases exist?	-	Go to Step 9	Go to Step 10
9	Evacuate the A/C system to a scavenging tank. Refer to Refrigerant Recovery and Recharging . Recharge the A/C system to specifications. Is the action complete?	-	Go to Step 14	-
10	The A/C system may contain too much moisture or air. Evacuate and recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging . Operate the A/C system and inspect the panel outlet air temperatures. Refer to Air Conditioning (A/C) System Performance Test (without PHT) Air Conditioning (A/C) System Performance Test (with PHT) . Are the panel outlet temperatures within the specified ranges of the A/C Performance Test Table?	-	Go to Step 15	Go to Step 11
11	The A/C system may contain too much refrigerant oil. Recover the refrigerant from the A/C system. Refer to Refrigerant Recovery and Recharging . Remove the accumulator. Refer to Accumulator Replacement . Drain and measure the refrigerant oil from the accumulator. Was more than the specified amount of refrigerant oil drained from the accumulator?	148 ml (5 oz)	Go to Step 12	Go to Step 13
12	Reinstall the accumulator. Refer to Accumulator Replacement . Flush the A/C system. Refer to Flushing . Recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Are the actions complete?	-	Go to Step 14	-
13	Add the specified amount of refrigerant oil to the accumulator. Refer to Refrigerant System Capacities . Install the accumulator. Refer to Accumulator Replacement . Recharge the A/C system. Refer to Refrigerant Recovery and Recharging . Are the actions complete?	-	Go to Step 14	-
14	Record the low and high side pressures and the I/P outlet air temperature. Compare the outlet temperatures to those listed in the A/C System Performance Chart. Refer to Air Conditioning (A/C) System Performance Test (without PHT) Air Conditioning (A/C) System Performance Test (with PHT) . Are the high and low side pressures and I/P panel outlet temperatures within specifications?	-	Go to Step 15	Go to Air Conditioning (A/C) System Performance Test (without PHT) Air Conditioning (A/C) System Performance Test (with PHT)
15	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 Symptoms - HVAC Systems - Automatic