A/C System Components Overview
Components Of Refrigerant Circuit
- All components of the refrigerant circuit submitted for quality observation are always to be sealed (use original sealing caps of replacement part).
- Replace damaged or leaking components of refrigerant circuit.
- To date, the following replacement parts (compressor, reservoir, receiver, evaporator and condenser) have been filled with nitrogen gas. This charge is being gradually discontinued. Little or no pressure equalization is therefore noticeable on unscrewing sealing plugs from replacement parts.
Arrangement of refrigerant circuit components and their influence on high and low pressure sides
On high pressure side are the condenser, receiver and restrictor or expansion valve to separate the high and low pressure liquid sides.
High pressure results from the restrictor or expansion valve forming a constriction and causing the refrigerant to accumulate, thus leading to an increase in pressure and temperature.
Excess pressure occurs if too much refrigerant or refrigerant oil is used, the condenser is contaminated, the radiator fan is malfunctioning, the system is blocked or in the event of moisture in the refrigerant circuit (icing-up of restrictor or expansion valve).
On low pressure side are the evaporator, reservoir, evaporator temperature sensor and compressor to separate high and low pressure gas sides
A drop in system pressure can be caused by loss of refrigerant, the restrictor or expansion valve (no constriction), a malfunctioning A/C compressor or an iced-up evaporator.
A/C compressor with A/C clutch
A/C compressor is driven by vehicle engine via a ribbed belt.
An electromagnetic clutch attached to A/C compressor provides the power link between the ribbed belt pulley and A/C compressor crankshaft with A/C system switched on.
A fuse installed in ribbed belt pulley of A/C compressor triggers the electromagnetic clutch when A/C compressor runs with resistance and protects the ribbed belt drive against overload.
The A/C compressor extracts the refrigerant gas from the evaporator, compresses it and relays it to the condenser.
NOTE:
- The A/C compressor contains refrigerant oil, which can be mixed with refrigerant R134a under any temperature.
- The refrigerant for which the A/C compressor is designed is listed on the manufacturers plate. A regulator valve regulates pressure within the specified range (control characteristics) on the low pressure side.
- So that the A/C compressor is not damaged when refrigerant circuit is empty, the A/C clutch is switched off and the A/C Compressor Regulator Valve N280 is no longer activated (A/C compressor runs at idle with engine).
A/C compressor without A/C clutch
A/C compressor is driven by vehicle engine via a ribbed belt.
An overload safeguard (bearing-type connection) installed in ribbed belt pulley of A/C compressor triggers when A/C compressor runs with resistance and protects the ribbed belt drive against overload.
The A/C compressor extracts the refrigerant gas from the evaporator, compresses it and relays it to the condenser.
NOTE:
- The A/C compressor contains refrigerant oil, which can be mixed with refrigerant R134a under any temperature.
- The refrigerant for which the A/C compressor is designed is listed on the manufacturers plate. A regulator valve regulates pressure within the specified range (control characteristics) on the low pressure side.
- In this A/C compressor, the regulator valve is activated from outside.
- Engine should only be started when the refrigerant circuit is completely assembled.
- The A/C compressor is equipped with a protected oil supply, this prevents A/C compressor damage in the event that the system is empty. This means that approx. 40 to 50 cu.cm of refrigerant oil remains in the A/C compressor.
A/C compressor without A/C clutch with torsion-elastic clutch
A/C compressor is driven directly by the power steering vane pump.
An overload safeguard is installed on drive shaft of A/C compressor which shears off when A/C compressor locks up so that power steering vane pump remains functional.
The A/C compressor extracts the refrigerant gas from the evaporator, compresses it and relays it to the condenser.
NOTE:
- The A/C compressor contains refrigerant oil, which can be mixed with refrigerant R134a under any temperature.
- The refrigerant for which the A/C compressor is designed is listed on the manufacturers plate. A regulator valve regulates pressure within the specified range (control characteristics) on the low pressure side.
- In this A/C compressor, the regulator valve is activated from outside.
- Engine should only be started when the refrigerant circuit is completely assembled.
- The A/C compressor is equipped with a protected oil supply, this prevents A/C compressor damage in the event that the system is empty. This means that approx. 40 to 50 cu.cm of refrigerant oil remains in the A/C compressor.
Condenser
The condenser conducts heat from compressed refrigerant gas to the ambient air.
This condenses the refrigerant gas to liquid.
Evaporator
The liquid refrigerant evaporates in the evaporator pipe coils. The heat required for this is drawn from the air flowing on the evaporator ribbing. The air cools off. Refrigerant evaporates and is extracted with the absorbed heat by the A/C compressor.
A defined amount of refrigerant is supplied to the evaporator by a restrictor or expansion valve. In systems with expansion valve, the flow is regulated so that only gaseous refrigerant escapes the evaporator outlet.
Reservoir
The reservoir collects the vaporized and gaseous mixture coming from the evaporator to ensure the A/C compressor only receives gaseous refrigerant. Gaseous refrigerant is formed from the vapor.
The refrigerant oil flowing in the circuit is not retained in the reservoir as it has an oil drilling.
Moisture which has entered the refrigerant circuit during repairs will be collected by a filter (desiccant bag) in the reservoir.
Gaseous refrigerant is extracted with oil by the A/C compressor.
NOTE:
- Replace the reservoir if refrigerant circuit has been open for a long time (beyond the normal repair time) and moisture has penetrated inside, or if required due to a specific complaint.
- Remove sealing plugs - A - and - B - only immediately prior to installing.
- A desiccant bag in an unsealed reservoir is saturated with moisture after a short period of time and unusable.
- When installing, note arrow for direction of flow if necessary.
Restrictor
The restrictor creates a constriction. This constriction reduces the flow and creates high and low pressure sides in the refrigerant circuit. Before the restrictor the refrigerant which is under a higher pressure is warm. After the restrictor the refrigerant which is under a low pressure is cold. Before the constriction there is a strainer for contaminants and after the constriction there is a strainer, to atomize the refrigerant before it reaches the evaporator.
NOTE:
- Arrow - A - on restrictor points to evaporator.
- Replace after each opening of the circuit.
- Note different versions.
Receiver
The receiver collects the liquid drops and then directs them in an uninterrupted stream to the expansion valve. Moisture which has entered the refrigerant circuit during repairs will be collected by the desiccant bag in the receiver.
NOTE:
- Replace the receiver if refrigerant circuit has been open for a long time (beyond the normal repair time) and moisture has penetrated inside, or if required due to a specific complaint.
- Only remove sealing plugs shortly before installation.
- A desiccant bag in an unsealed receiver is saturated with moisture after a short period of time and unusable.
- When installing, note arrow for direction of flow if necessary.
The new generation of receivers are installed directly on the condenser and possess a dryer cartridge.
NOTE:
- Replace the dryer cartridge if refrigerant circuit has been open for a long time (beyond the normal repair time) and moisture has penetrated inside, or if required due to a specific complaint.
- Only unpack dryer cartridge immediately prior to installation.
- Dryer cartridge in unsealed packaging is saturated with moisture after a short period of time and unusable.
Expansion valve
The expansion valve atomizes the streaming refrigerant and controls the flow quantity so that the vapor is gaseous only at the evaporator outlet, depending on the heat transmission.
O-ring seals
These rings seal off the connection points between individual components of the refrigerant circuit.
Only O-rings that are resistant to refrigerant R134a and refrigerant oil must be installed. Make sure they are original replacement parts.
O-ring seals:
- Always use only once.
- Make sure diameters - a - and - b - are correct.
- Lubricate with refrigerant oil before installing.
NOTE: The color coding of O-rings for the R134a refrigerant circuits has been discontinued. Colored and black O-rings are used.
Refrigerant circuit pipes and hoses
The mixture of refrigerant oil and refrigerant R134a corrodes certain metals (e.g. copper) and alloys and dissolves some hose materials. Therefore use original replacement parts only.
Pipes and hoses are joined together by threaded connections or via special plug connectors.
NOTE: Observe specified torques for threaded connections, use appropriate release tools for plug connectors.
Pressure relief valve
Pressure relief valve is installed on A/C compressor or receiver.
At a pressure of approx. 38 bar positive pressure, valve opens and closes again once pressure has dissipated (approx. 30 bar).
Refrigerant does not escape completely.
Depending on the version, a transparent plastic disc may be installed which breaks off as soon as the valve is activated.