Mechanically Driven A/C Compressor
The A/C compressor is driven by a ribbed belt -B- or an input shaft, which is driven by the vehicle engine.
A/C Compressor with A/C Clutch -N25-
An electro-magnetic clutch -A- attached to the A/C compressor provides the power link between the belt pulley -B- and A/C compressor crankshaft when the A/C system is switched on.
An overload safeguard attached to the clutch plate or in the A/C compressor solenoid coil is tripped if the compressor does not move freely, thus protecting the belt drive or the drive unit against overload.
So that the A/C compressor does not get damaged when the refrigerant circuit is empty, the A/C Compressor Regulator Valve -N280- and the A/C Clutch -N25- is no longer activated (the A/C compressor only runs when the A/C Clutch A/C Clutch -N25- is activated at idle with the engine).
An A/C compressor with an A/C Clutch A/C Clutch -N25- (without A/C Compressor Regulator Valve A/C Compressor Regulator Valve -N280-)is not activated by an empty refrigerant circuit and not driven.
A/C Compressor without A/C Clutch -N25-
- An overload safeguard attached to the belt pulley -B- or in the A/C compressor drive unit is tripped if the compressor does not move freely, thus protecting the belt drive or the drive unit against overload.
- An A/C compressor with A/C Compressor Regulator Valve -N280- (without A/C Clutch A/C Clutch -N25-)is switched to internal lubrication by way of a valve when the refrigerant circuit is empty.
On A/C compressors without an A/C Clutch -N25-, he engine is only to be started if the refrigerant circuit is completely assembled.
So that the A/C compressor does not get damaged when the refrigerant circuit is empty, the A/C Compressor Regulator Valve -N280- is no longer activated (A/C compressor runs at idle with engine).
All A/C Compressors
The A/C compressor extracts the refrigerant gas from the evaporator, compresses it and sends it to the condenser.
The A/C compressor contains refrigerant oil, which can be mixed with refrigerant R1234yf at any temperature.
The type plate lists the type of refrigerant required for the A/C compressor. A regulator valve regulates the pressure on the low pressure side within the specified range (control characteristic). Refer to Refrigerant Circuit (vehicle-specific service information).
Depending on the version of the A/C compressor different refrigerant oils are filled in the A/C compressor. Refrigerant oil which was only developed for the refrigerant R134a, may not be used for the refrigerant R1234yf. Refer to APPROVED REFRIGERANT OILS AND REFRIGERANT OIL CAPACITIES .
A/C compressors with or without a A/C Clutch -N25- are currently activated from the outside by a A/C Compressor Regulator Valve -N280- -C-.Refer to Refrigerant Circuit (vehicle-specific service information).
The refrigerant for which the A/C compressor is designed is listed on the manufacturer's plate. An A/C Compressor Regulator Valve -N280- regulates the pressure on the low pressure side within the specified range (control characteristic). Refer to Refrigerant Circuit (vehicle-specific service information).
The A/C Compressor Regulator Valve -N280- is activated from the outside. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system.
The engine on a vehicle with an A/C compressor without an A/C Clutch -N25- cannot be activated, when the refrigerant circuit is under vacuum (for example when evacuating). Refer to WORKING WITH A/C SERVICE STATION .
The engine can be restarted on a vehicle with an A/C compressor without a A/C Clutch -N25- when the refrigerant circuit is completely assembled.
So that the A/C compressor does not get damaged when the refrigerant circuit is empty, the A/C Compressor Regulator Valve -N280- is no longer activated (the A/C compressor runs at idle with engine) if the refrigerant circuit is too low (smaller than 2 bar (29.01 psi)).
An A/C compressor with A/C Compressor Regulator Valve -N280- is switched to internal lubrication by way of a valve when the refrigerant circuit is empty.
Depending on the A/C compressor version, there may be a valve installed on the high pressure side of the A/C compressor, which prevents the liquid refrigerant from flowing back into the A/C compressor after the A/C system is turned off. If an A/C compressor with this valve is installed in a vehicle with a refrigerant circuit having an expansion valve, then it may take some time until the pressure in the high pressure side decreases (the expansion valve is cold and the pressure in the low pressure side quickly increases after it is turned off, the expansion valve closes and the refrigerant can flow slowly to the low pressure side). If the A/C compressor is switched on, the pressure on the low pressure side decreases, the expansion valve opens and the refrigerant can flow to the low pressure side.
On A/C compressors with an electro-magnetic clutch -A- and a regulator valve -C-, he electro-magnetic clutch -A- is, for the most part, only activated when the regulator valve -C- is also activated. Refer to Refrigerant Circuit (vehicle-specific service information).