A/C Refrigerant System, Components
A/C Refrigerant System, Components
A/C Compressor
The compressor is driven via a ribbed belt on the engine when the A/C clutch (mounted as part of the compressor) is engaged (A/C ON).
Low pressure refrigerant gas from the evaporator is suctioned and compressed by the compressor. After compression, the refrigerant gas (now high pressure) flows to the Condenser.
NOTE:
- The compressor contains PAG refrigerant oil that is mixable under all temperatures with refrigerant R-134a.
- A label on the compressor indicates that the compressor is for use in R-134a systems only.
Condenser
The Condenser transfers heat from the compressed refrigerant gas to the outside air which causes the refrigerant to change state from a gas to a liquid.
Evaporator
Liquid refrigerant entering the evaporator absorbs heat from air passing through the evaporator fins and cools the air. As the refrigerant absorbs heat it turns to vapor and is suctioned by the compressor.
Receiver drier
The receiver drier -G- acts as a refrigerant reservoir for the system as the high pressure liquid refrigerant flows to the expansion valve.
Any moisture contaminants in the system is absorbed by the desiccant in the receiver drier.
CAUTION:
- Do not remove sealing caps until ready to install new receiver drier.
- If caps are removed too soon, the desiccant becomes saturated with moisture after a very short time. If this occurs, the receiver drier must be replaced.
Expansion valve
The expansion valve -B- restricts and regulates refrigerant flow, thus lowering refrigerant temperature and pressure as it flows to the evaporator.
The TT uses a thermo-dynamic expansion valve design. It regulates refrigerant flow as follows: As cooling demands increase (high outside temperatures), the temperature of the refrigerant leaving the evaporator and entering the expansion valve also increases. Here, the refrigerant temperature is sensed by a gas filled thermo-pressure chamber inside the expansion valve. The thermo-pressure chamber acts on a membrane attached to a conventional ball/orifice valve positioned in the expansion valve refrigerant circuit from the Condenser to the evaporator. As the refrigerant temperature increases, the thermo-pressure membrane opens the ball/orifice valve, allowing an increase in refrigerant flow to the evaporator. Increased cooling capacity is achieved as a result. As the refrigerant temperature exiting the evaporator decreases, the thermopressure membrane closes the ball/orifice valve, and restricts refrigerant flow to the evaporator. This cycle ensures consistent cooling efficiency, regardless of outside temperature.
NOTE:
- Always ensure that the expansion valve insulation is in place and is not damaged.
- Due to the thermo-dynamic design of the expansion valve, the operating parameters of the valve are adversely affected when the insulation is missing or improperly installed. A decrease in cooling efficiency will result.
O-Rings
O-rings seal the connections between components of the A/C system.
Use only O-rings which are compatible with R-134a refrigerant and refrigerant (PAG) oil. Refer to the most recent parts information when obtaining new O-rings.
O-rings are recognized by colors (currently red, green or violet). Under certain conditions, black O rings may also be installed in production.
NOTE:
- Use O-rings only once and always replace.
- Handle the O-rings only in a clean working environment.
- Always use correct size O-rings (dimensions -a- and -b-).
- Lubricate the O-rings with refrigerant (PAG) oil before installing.
- Always make sure to properly install the O-rings on line/component mounting flanges/grooves.
- O-ring and torque specifications also apply to the threaded connections in the A/C lines.
Hoses and lines
The mixture of refrigerant oil (PAG oil) and refrigerant R-134a attacks some metals and alloys (for example, copper) and breaks down certain hose material. Use only hoses and lines which are identified with the lettering "R-134a."
Hoses and lines are secured with threaded connections. Always properly torque hose and line connections.
Pressure relief valve
The pressure relief valve is mounted on the compressor. At approx. 38 bar (551 psi), the valve opens to vent excessive pressure. When system pressure is reduced to approx. 30-35 bar (435-508 psi), the valve closes to prevent total refrigerant loss.