A/C Update
Spring Service: Do’s and Don’ts in A/C Repair
By Larry Carley, technical editor
As vehicle owners in many parts of the country begin using their air conditioning systems for the first time this year, some will be surprised to find their A/C system is not functioning properly or isn’t blowing out cold air like the summer past.
The following is a recap of common A/C system problems, followed by real-life A/C system problems from 2003-’05 General Motors SUVs and a poor performing climate system on a Toyota truck.
Causes for A/C Repairs
A/C compressors are usually the most expensive A/C component to replace, followed by condensers and evaporators. So it’s very important to make sure (1) the compressor is really bad and needs to be replaced, (2) the cause of the compressor failure has been identified and fixed so the new compressor does not fail for the same reason, and (3) the new compressor is installed properly and lubricated with the correct type of compressor oil.
The most common cause of compressor failure is inadequate lubrication. This may be the result of a refrigerant leak that allows compressor oil to leak out of the system. Typical leak points are hoses, hose and pipe connections (O-rings and flange gaskets), the evaporator, condenser or the compressor shaft seal. Leak detection dye or an electronic leak detector should be used to find the leak so it can be repaired.
Proper Lubrication and Debris
Lubrication problems can also be caused by a blockage (typically the orifice tube) that prevents refrigerant and oil from circulating through the A/C system.
Using the wrong type of compressor oil for the application or the wrong amount can also lead to premature wear and failure. There are various grades of PAG oil, and using the wrong grade can cause problems. Always use the type of PAG oil specified by the compressor manufacturer or vehicle manufacturer. Use only the amount specified for the compressor. Adding too much oil can cause cooling problems.
Mineral-based compressor oil is only for older vehicles (pre-1995) with R-12 compressors, and should never be used with a compressor in an R-134 A/C system.
A compressor may also fail if there is sludge or debris inside the A/C system. Moisture contamination of the refrigerant can form acids that attack metal surfaces and form sludge inside the system. Over time, this can gum up and damage the compressor. If the system contains any sludge or debris, the hoses, evaporator and condenser should all be flushed out to remove the contaminants.
Note: Some condensers cannot be flushed due to the way they are constructed, so replacement is necessary if the condenser is contaminated.
A compressor may also have to be replaced if it is leaking, making excessive noise or not working correctly because of an internal valve or piston failure. Some compressors are naturally noisier than others, but loud knocking noises can sometimes be caused by air in the system. The cure in this case is not to replace the compressor, but to recover the refrigerant from the system, then vacuum purge the system for 30 minutes to an hour with an A/C vacuum pump to remove the unwanted air. If the compressor is still making noise after the system has been purged and recharged, it probably needs to be replaced.
When a compressor fails, it may spew out metallic debris. Most of the junk ends up in the condenser, but some may travel as far as the orifice tube or be blown back into the suction hose. If this junk is not flushed out of the system, it can be sucked into the new compressor and cause it to fail, also.
Additional Parts Replacement
When a compressor is replaced, the accumulator or receiver/drier also should be replaced. The accumulator or receiver/drier contains a bag of desiccant that absorbs moisture. This helps to protect the A/C system against sludge. But over time, the desiccant becomes saturated and cannot hold any more water. If the A/C system has been opened up for repairs, or has lost its charge of refrigerant, humidity in the outside air can enter the system and overload the desiccant. That’s why it needs to be replaced.
Another component that should also be changed when replacing a compressor is the orifice tube. This small plastic tube meters refrigerant into the evaporator. If it plugs up, it can block the flow of coolant, causing the A/C to stop blowing cold air. It can also starve the new compressor for lubrication because the oil circulates with the refrigerant.
A couple of preventive measures can also be taken to protect a new compressor. One is to install an in-line filter in the high-pressure liquid line to catch any debris that might come out of the condenser. Another is to install an inlet screen filter in the suction hose to stop any debris from being sucked into the compressor.
Other A/C components that may also have to be replaced when changing a compressor include the magnetic clutch (if it is worn or slipping), the drive belt and A/C hoses. Refrigerant that contains leak detection dye can be used to recharge the system. After the dye circulates awhile, it will reveal any leaks that might have been missed and need to be repaired.
GM Truck HVAC Out of Control
By Rich Diegle, ALLDATA Senior Automotive Editor
Some GM truck and SUV owners may comment that they cannot control the heating, ventilation and air conditioning (HVAC) system. Others may comment that the HVAC system defaults to the Defrost mode.
If a technician checks for diagnostic trouble codes (DTC), they could find that the following DTCs have set:
B0229 - Recirculation Actuator
B0414 - Left Air Temperature Actuator
B0424 - Right Air Temperature Actuator
B3770 - Mode Actuator Cause
The problem may be that the HVAC actuator harness has contacted a sharp edge on the instrument panel support brace, causing a rub through condition and a grounding of the actuator control and/or feedback circuits.
Models affected: 2003-’05 Cadillac Escalade, Escalade ESV, Escalade EXT; Chevrolet Avalanche, Silverado (pictured), Suburban, Tahoe; and GMC Sierra, Yukon, Yukon XL- To repair the problem, locate the HVAC actuator harness contact point shown by the arrow in Figure 1.
Note: The illustration is of the instrument panel with the instrument panel compartment door opened and folded downward. The actuator harness is located in the left side of the opening in the instrument panel.
Inspect the HVAC actuator harness for contact with the instrument panel support brace. Repair any damage to the actuator harness wiring.
Install a protective plastic conduit over the harness.
Install friction tape over the sharp edge of the instrument panel brace to insulate it.
Clear the diagnostic trouble codes and verify proper HVAC system operation.
Fixing Poor-Performing Toyota Sequoia A/C
By Rich Diegle, ALLDATA Senior Automotive Editor
Some 2001-’04 Sequoia and 2000-’04 Tundra vehicles may exhibit a condition where the air conditioning system does not sufficiently cool the cabin. Vehicle owners will notice the problem more often when ambient temperatures exceed 80° F (26.6° C). Before performance-testing the air conditioning system, check the adjustment of the water control valve cable. Refer to the Repair Procedure for the details.
Repair Procedure- Turn the temperature control knob to the full cold position.
Inspect the clearance between the water control valve lever and the lever stop. See Figure 2. If the lever does not contact the lever stop, proceed to step 3.
If the lever does not contact the lever stop:
a. Disengage the cable retaining clip.
b. Pull up on the cable sheath until the water control valve lever contacts the lever stop.c. Re-fasten the cable retaining clip.
Cycle the temperature control knob several times and confirm proper water control valve adjustment. See Figure 3.
MACS Launches New Website
Lansdale, PA — Visit www.macsw.org and experience a more user-friendly and efficient web environment. MACS Mobile Air Conditioning Society Worldwide website to the membership and certification database which is the backbone of the association information management system. MACS members can enjoy member-only content that includes a summary of member business advantages, archived convention presentations, ACTION magazine articles and back issues of the MACS Service Reports.
All visitors can find a wealth of information regarding mobile air conditioning technical and regulatory information, training and convention events and resources for industry professionals, student technicians and consumers.
ASE Updates Refrigerant Program
Leesburg, VA — The National Institute for Automotive Service Excellence (ASE) has updated its Section 609, EPA-approved Refrigerant Recovery and Recycling Program. This latest version includes the EPA’s adoption of a new standard for refrigerant handling equipment, along with updated awareness of acceptable and unacceptable refrigerants.
The new standard, J2788, from the Society of Automotive Engineers (SAE), supersedes an older standard, J2210. The J2788 standard specifies more stringent performance requirements for refrigerant handling equipment. J2788 only applies to equipment built after December 31, 2007. “Technicians and shop owners needn’t panic over the adoption of this new standard by the EPA,” said Tim Zilke, ASE president. “The action doesn’t automatically make older equipment obsolete, nor does it make the use of that older equipment a service procedure violation in the eyes of the EPA.”
As a reminder, technicians should not confuse the ASE Refrigerant Recovery and Recycling Program with the ASE Heating and Air Conditioning (A7, H7, S7 and T7) certification. Only the ASE Refrigerant Recovery and Recycling program meets Section 609 requirements by the U.S. EPA for motor vehicle air conditioning service.