EI07200 - HVAC Performance, A/C Not Cool, A/C Compressor Noise

This bulletin is being revised to update the diagnostic information. Please discard Corporate Bulletin Number 07-01-39-005 (Section 01 -- HVAC).

Important: If the customer did not bring their vehicle in for this issue, do not proceed with this bulletin. ONLY CONTACT THE ENGINEER IF DIAGNOSIS LEADS TO AN A/C REPAIR.

Some customers may comment that the vehicle's A/C is not cooling or is not cold enough and/or the A/C compressor is noisy.

DO NOT REPLACE THE A/C COMPRESSOR.

GM Engineering is attempting to determine the root cause for the concern of A/C not cooling and/or compressor noise. A high percentage of A/C compressors being returned to the Warranty Parts Center (WPC) show no trouble found. Engineering has a need to gather information on vehicles, PRIOR to repair, that may exhibit this condition. Document the following information on the repair order:

For Concerns of Poor Performance or Not Cold:

1. Only proceed with this bulletin if the vehicle currently exhibits the condition. Describe the specific customer's concern.
2. Compare the cooling performance to that of another vehicle under the same operating conditions and confirm if the performance is the same or significantly unusual (no cooling performance).
3. Perform the A/C System Performance Test according to the procedure listed in SI.
4. Record the ambient air temperature displayed on the J-43600.
5. Record the high and low side STATIC pressure readings.
6. Record the relative humidity and ambient air temperature at the time of the test.
7. Record the outlet air temperatures, high side and low side pressures taken while performing the A/C Performance Test.
8. What were the results from the A/C Performance Test?

•	System OK - no further repairs required.

•	A/C Diagnostics Pressure Zone A - proceed with Step 9.

•	A/C Diagnostics Pressure Zone B - proceed with Step 10.

•	A/C Diagnostics Pressure Zone C - proceed with Step 11.

•	A/C Diagnostics Pressure Zone D - proceed with Step 12.

9. If the A/C Performance Test leads to the A/C Diagnostics Pressure Zone A:

•	What was the difference in discharge temperature of the center panel outlets?

•	Are the A/C system output temperatures good at first, but then turn warm during extended drives?

•	Was the A/C system found to be undercharged? If so, was a leak test performed and a leak found?

•	Was the A/C system found to possibly be contaminated?

•	If the system was evacuated and recharged, are the panel outlet temperatures within specification?

•	What repair corrected the concern?

•	Proceed to Step 13.

10. If the A/C Performance Test leads to the A/C Diagnostics Pressure Zone B:

•	After continued operation of the A/C system, do the low and high side pressures equalize or become static?

•	Did the A/C system have low refrigerant charge?

•	Was the AC compressor malfunctioning due to contamination?

•	What repair corrected the concern?

•	Proceed to Step 13.

11. If the A/C Performance Test leads to the A/C Diagnostics Pressure Zone C:

•	Are the cooling fans on and operating properly?

•	Inspect and note any of the following conditions and make any necessary repairs.

-	restricted air flow

-	damaged condenser cooling fins

-	missing or misaligned air baffles

•	What repair corrected the concern?

•	Proceed to Step 13.

12. If the A/C Performance Test leads to the A/C Diagnostics Pressure Zone D, what repair corrected the concern?

•	Were any abrupt drops in temperature detected along the surfaces of these components?

-	compressor discharge hose

-

condenser

-	liquid line between the condenser and expansion device.

•	Was a restriction detected? If so, where?

•	Was the system leak tested? Any leaks found? If so, where?

•	What corrected the concern?

•	Proceed to step 13.

13. Immediately contact the following engineer to report the findings ONLY IF A CONDITION IS IDENTIFIED THAT REQUIRES A/C SYSTEM REPAIR. Have all A/C Performance Testing information available when contacting the engineer. If the A/C compressor is suspect, be prepared with all repair order information.

For Concerns of A/C System Noisy During Slow Parking Lot Maneuvers:

1. Replace the HVAC hose with suction line P/N 20757021.
2. Evaluate the vehicle to determine if the customer's concern has been corrected.
3. If the customer's concern has NOT been corrected, contact engineer Mike Monroe at 248-467-0529.

If the customer's concern HAS been corrected, submit a Field Product Report -- refer to TSB 02-00-89-002G.

The following part should be replaced ONLY to correct the concern of A/C Noisy:

Select the appropriate labor operation based on the repair made: