Climate Control System: Notes

• Always wear safety goggles when repairing an air conditioning system. 
• Avoid contact with liquid refrigerant R-134a. R-134a vaporizes at approximately -25°C (-13°F) under atmospheric pressure and it will freeze skin tissue. 
• Never allow refrigerant R-134a gas to escape in quantity in an occupied space. R-134a is non-toxic, but it will displace the oxygen needed to support life. 
• Never use a torch in an atmosphere containing R-134a gas. R-134a is non-toxic at all normal conditions, but when it is exposed to high temperatures, such as a torch flame, it decomposes. During decomposition it releases irritating and toxic gases (as described in the MSDS sheet from the manufacturer). Decomposition products are hydrofluoric acid, carbon dioxide and water. 
• Do not allow any portion of the charged air conditioning system to become too hot. The pressure in an air conditioning system rises as the temperature rises and temperatures of approximately 85 °C (185 °F) can be dangerous. 
• Allow the engine to cool sufficiently prior to carrying out maintenance or serious burns and injury can occur. 

• The A/C refrigerant of all vehicles must be identified and analyzed prior to refrigerant charging. Failure to do so can contaminate the shop bulk refrigerant and other vehicles. 
• Do not add R-12 refrigerant to an A/C system that requires the use of R-134a refrigerant. These two types of refrigerant must never be mixed. Doing so can damage the A/C system. 
WARNING: It is dangerous to charge the system with the engine running at the high side service port. 
• Charge the A/C system with R-134a refrigerant gas while the engine is running only at the low-pressure side to prevent refrigerant slugging from damaging the A/C compressor. 
• Use only R-134a refrigerant. Due to environmental concerns, when the air conditioning system is drained, the refrigerant must be collected using refrigerant recovery/recycling equipment. Federal, State/Provincial and/or local laws REQUIRE that R-134a be recovered into appropriate recovery equipment and the process be conducted by qualified technicians who have been certified by an approved organization, such as ASE, MACS, HRAI, etc. Use of a recovery machine dedicated to R-134a is necessary to reduce the possibility of oil and refrigerant incompatibility concerns. Refer to the instructions provided by the equipment manufacturer when removing refrigerant from or charging the air conditioning system. 
• Refrigerant R-134a must not be mixed with air for leak testing or used with air for any other purpose above atmospheric pressure. R-134a is combustible when mixed with high concentrations of air and higher pressures. 
• A number of manufacturers are producing refrigerant products that are described as direct substitutes for Refrigerant R-134a. The use of any unauthorized substitute refrigerant can severely damage the A/C components. If repair is required, use only new or recycled Refrigerant R-134a. 

• Never open or loosen a connection before recovering the refrigerant. 
• When loosening a connection, if any residual pressure is evident, allow it to leak out before opening the fitting. 
• Evacuate a system that has been opened to install a new component or one that has discharged through leakage before charging. 
• Seal open fittings with a cap or plug immediately after disconnecting a component from the system. 
• Clean the outside of the fittings thoroughly before disconnecting a component from the system. 
• Do not remove the sealing caps from a new component until ready to install. 
• Refrigerant oil will absorb moisture from the atmosphere if left uncapped. Do not open an oil container until ready to use and install the cap immediately after using. Store the oil in a clean, moisture-free container. 
• Install a new O-ring seal before connecting an open fitting. Coat the fitting and O-ring seal with mineral oil before connecting. 
• When installing a refrigerant line, avoid sharp bends. Position the line away from the exhaust or any sharp edges that can chafe the line. 
• Tighten threaded fittings only to specifications. The steel and aluminum fittings used in the refrigerant system will not tolerate overtightening. 
• When disconnecting a fitting, use a wrench on both halves of the fitting to prevent twisting of the refrigerant lines or tubes. 
• Do not open a refrigerant system or uncap a new component unless it is as close as possible to room temperature. This will prevent condensation from forming inside a component that is cooler than the surrounding air. 

The electronic manual temperature control (EMTC) system heats or cools the vehicle depending on the EMTC control panel selection.

• The EMTC control panel selections determine heating or cooling, air distribution and enables blower motor operation.
• The temperature control setting determines the air temperature.
• The blower motor switch varies the blower motor speed.
• During A/C operation the system also reduces the relative humidity of the air.
• The driver side and passenger side temperature settings can be individually controlled. (Dual-zone EMTC only.)

The dual-zone electronic automatic temperature control (EATC) system maintains the selected vehicle interior temperature by heating and/or cooling the air.

• During A/C operation the system also reduces the relative humidity of the air.
• The driver may override the automatic mode of operation.
• The temperature control setting determines the air temperature.
• The blower motor control override buttons vary the blower motor speed.
• The driver side and passenger side temperature settings can be individually controlled.