Subject: | Diagnostic Information To Consider Before Air Conditioning Compressor Replacement |
Models: | 1993-2004 Passenger Cars and Light Duty Trucks |
This bulletin is being revised to add the 2004 model year and add information
for clarification. Please discard Corporate Bulletin Number 01-01-38-013 (Section
01 -- HVAC).
A recently completed analysis of air conditioning (A/C) compressors that had
been replaced for noise, vibration and insufficient cooling concerns has indicated
a high number of "no trouble found" results. Further studies have shown
that the root cause of the customer concerns that might lead to a compressor replacement
was often a state of refrigerant charge issue or in another area or system of the
vehicle. The A/C system refrigerant charge level, either high or low, has been found
to be a major contributor to unnecessary compressor replacement. The ability of the
ACR 2000 Refrigerant Recycling/Recharging Tool to recover and measure the weight
of the A/C system refrigerant charge will help the technician make a more accurate
diagnosis of a charge level concern prior to any component replacement.
A thorough visual inspection should always be performed before any tests or
repairs are done. Doing so may find an obvious problem that will save time and eliminate
the need for extensive diagnosis. Some additional items, as listed below, should
be considered before a compressor is replaced for noise, vibration or insufficient
cooling concerns.
• | The compressor mounting bolts, brackets or braces may be loose or missing. |
• | The compressor drive belt may be frayed, loose or misaligned. |
• | The A/C refrigerant lines may be grounding out on body, chassis or engine
components. This may allow noise and vibration to be transmitted into the passenger
compartment. |
• | The air flow through the condenser may be insufficient. |
- | The condenser fins may be bent or filled with debris. |
- | The space between the condenser and radiator may be filled with leaves
or debris. |
- | The cooling fans may be inoperative or not performing as designed. |
- | The installation of aftermarket accessories may alter or restrict the
air flow through the condenser. |
• | Inspect for missing or mispositioned air deflectors, baffles,
seals and shrouds. |
• | The compressor cycling switch may not be operating correctly. This may
allow the evaporator core to freeze up or the compressor may not stay engaged long
enough for proper system pressures to develop. |
• | The air flow through the evaporator core may be restricted. |
- | The cabin filter may be plugged. |
- | The evaporator core may be covered with debris. |
- | The cowl air inlet leaf screen may by plugged. |
• | The A/C system may be overcharged or undercharged with refrigerant. The
A/C system charge weight can be measured with the ACR 2000 after a refrigerant recovery
is done. |
• | The A/C system may have an improper amount or incorrect type of refrigerant
oil. Only GM approved refrigerant oils should be used. |
• | An A/C system sealer is not approved for use in GM vehicles. |
• | The vehicle's refrigerant may be contaminated or contain an excessive
amount of air. The vehicle's A/C system may have been charged with an unapproved
refrigerant. The refrigerant identifier on the ACR 2000 should alert the technician
to these conditions. |
• | The orifice tube or thermostatic expansion valve (TXV) may be restricted,
plugged or inoperative. |
• | The capillary bulb on the TXV must be properly positioned so that the
valve will provide proper refrigerant flow. |
• | The desiccant bag in the accumulator may have failed, allowing debris
to circulate in the A/C system. |
• | The A/C system charge weight may have been changed. Components with an
updated design may have been released. A check for service bulletins applicable to
the vehicle being worked on should always be done. |
• | A check for diagnostic trouble codes in all the control modules on the
vehicle should be done. Some trouble codes will disable compressor operation after
they have set. They must be repaired and cleared before compressor operation is allowed. |
• | Verify that the engine is not operating with a low unstable idle, and
that the engine is operating within the compressor engagement parameters (for example;
the engine may be overheating or it may be too cold for compressor engagement). |
• | The diagnostic procedures in the HVAC section of the Service Manual should
be performed as written to prevent the misdiagnosis of a customer concern. The HVAC
Diagnostic System Check and the A/C System Performance Test are written for a specific
model only. They are not generic charts. They follow a logical order with detailed
instructions on how to perform each step. |
• | The Technical Assistance Center may be contacted for additional help
and the latest information on any unusual concerns. |
When a thorough HVAC system diagnosis indicates that the compressor should
be replaced, follow the procedure in the appropriate Service Manual. The oil balance
instructions are an important part of the replacement procedure. The correct refrigerant
oil, as listed in the Service Manual, must be used in the new compressor. It is recommended
that a suction screen filter be installed on Delphi Harrison compressors that do
not already have one. The suction screen filter is not approved for use on compressors
from other manufacturers. Refer to Corporate Bulletin Number 01-01-39-003A for more
information on A/C suction screen kit repair recommendations and procedures. If the
compressor has had a catastrophic internal failure, an inline filter may be required
to capture the large amount of debris that may be found to be circulating in the
A/C system. In addition, the A/C system may require flushing. Refer to Corporate
Bulletin Number 01-01-38-006B for more information on flushing
procedures and recommendations.
The addition of fluorescent refrigerant leak dye to the A/C system is recommended
if the vehicle does not have it installed already. Some vehicles have leak dye installed
at the assembly plant and this will be indicated on the A/C charge label. Refer to
Corporate Bulletin Number 00-01-38-009B for more information. If
leak dye has been added during a previous repair and has been in the vehicle for
more than three years, it is recommended that additional dye be added. Finally, a
leak check of the entire A/C system should be performed before the vehicle is returned
to the customer.
Important: For all GM paid repairs, the charge summary
printout from the ACR 2000 is still required to be attached to the shop copy of the
repair order. The warranty code must be submitted in the warranty claim information
in the comment field. This code provides valuable information about the repair to
General Motors for product quality improvement.