EI07139 - HVAC Performance, A/C Not Cool, A/C Compressor Noise (Engineering Information)

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 the 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:

1. Does the vehicle currently exhibit the condition? If the condition is for A/C compressor noise, proceed to step 14. Otherwise continue with step 2.
2. What A/C system (RPO) is the vehicle equipped with?
3. 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).
4. Perform the A/C Performance System Test according to the procedure listed in SI.
5. Record the ambient air temperature displayed on the J 43600.
6. Record the high and low side STATIC pressure readings.
7. Record the relative humidity and ambient air temperature at the time of the test.
8. Record the outlet air temperatures, high side and low side pressures taken while performing the A/C Performance Test.
9. What were there results from the A/C Performance Test?

•	System OK -- no further repairs required.

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

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

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

•	A/C Diagnostics Pressure Zone D -- proceed with Step 13.

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

•	What was the difference in discharge temperature between the right and left 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 14.

11. 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 A/C compressor malfunctioning due to contamination?

•	What repair corrected the concern?

•	Proceed to Step 14.

12. 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 14.

13. 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 14.

14. Immediately contact the following engineers 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.

Select the appropriate labor operation based on the repair made: