A/C Refrigerant System, Component Overview

A/C Refrigerant System, Component Overview

Compressor







The compressor is driven via a belt on the engine when the A/C clutch engages (A/C "ON").

Low-pressure refrigerant gas from the evaporator is compressed by the compressor. After compression, the refrigerant gas (now high-pressure) flows to the condenser.


NOTE:
- The compressor contains refrigerant oil that is mixable under all temperatures with the refrigerant.
- A label on the compressor indicates that compressor is for 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.


NOTE: The condenser for the R-134a refrigerant system is identified with a green label.


Restrictor







The restrictor restricts and controls refrigerant flow to the evaporator thus lowering refrigerant temperature and pressure.

Upstream of the restrictor, the refrigerant is hot and under high pressure. Downstream of the restrictor, the refrigerant is cold and under low pressure.

A strainer located upstream of the restrictor filters out any dirt or particles. Another strainer downstream of the restrictor atomizes the refrigerant before it enters the evaporator.


NOTE: Insert restrictor so that arrow -A- points to evaporator.


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 then is suctioned by the compressor.

Accumulator







The accumulator traps the mixture of refrigerant vapor (liquid) and gas as coming from the evaporator. The accumulator acts as a refrigerant reservoir for the system and ensures that the compressor only suctions gaseous refrigerant. Any moisture in the refrigerant system is absorbed by drier desiccant in the accumulator.


NOTE:
- Replace the accumulator each time the refrigerant circuit is opened.
- Do not remove sealing caps -A- and -B- until just prior to installation. The drier dessicant in non sealed accumulators becomes saturated with moisture and there for unusable.


A/C system 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 that are identified with a green mark (stripe) or the lettering "R-134a".

Hoses and lines are fastened together with threaded couplings/fittings and are retained (to bodywork or components) with specially isolated hose clamps.


NOTE:
- During servicing, all couplings, fittings and related fasteners must be torqued to specifications.
- Ensure that only special tools (as specified) are used while servicing.


O-rings







O-rings seal connections between A/C system components.


NOTE:
- Always use correct size 0-rings (dimensions -a- and -b-).
- Do not reuse O-rings, always replace. Use only new O-rings that are compatible with R-134a refrigerant and refrigerant (PAG) oil on R-134a systems.
- O-rings for use only on R-134a systems are color coded: red, green, violet or black.
- Lubricate O-rings with the appropriate refrigerant oil before installing (only use PAG oil).


Pressure relief valve







The pressure relief valve is mounted on the compressor or compressor inlet/outlet manifold. At pressures above 40 bar (580 psi), the pressure relief valve opens to vent excessive pressure. When the system pressure is reduced, the valve closes to prevent total refrigerant loss.

On some models, a cap on the pressure relief valve will pop out if the valve has opened.

A/C pressure switch -F129-







The A/C pressure switch is a combination switch (two switching components) that protects refrigerant circuit components from malfunctioning due to excessive or insufficient refrigerant system pressures.
- Switch part between terminals 1 and 2 switches off the A/C clutch -N25- when the system pressure is too high or when there is not enough refrigerant in the system
- Switch part between terminals 3 and 4 switches coolant fan -V7- to the next higher fan speed when system pressures increase.