Refrigerant Shut-Off Valves
Shut-Off Valve with Two Switching States (Open or Closed).
- There are different versions of the shut-off valve with different functions and with different names. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).
- If the shut-off -A- is not activated by the electronics, it is open and lets the refrigerant flow through.
- The shut-off valve -A- is installed on vehicles with a high-voltage system. It is activated when no A/C system operation is desired for the passenger compartment or for the Hybrid Battery Unit -AX1-, but is necessary for battery cooling.
- Observe the arrow -B- attached to the shut-off valve -A-, which shows the flow direction of the refrigerant (from the condenser to the evaporator in the heater and A/C unit)
- The solenoid coil -C- installed on the shut-off valve -A- is activated depending on the vehicle from different control modules. Refer to the appropriate Wiring Diagram and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function for the A/C system and the battery regulation.
- If, for a vehicle with two evaporators (one in the heater and A/C unit and one in the battery cooling module, for example on the Q5 Hybrid), the measured temperature on one of the evaporators corresponds to the specified value or the specified value falls short, but does not reach the required specified value on the other evaporator, the following adjustment is performed: The respective control module activates the electric A/C compressor with increased speed (thereby increasing the A/C system cooling output and decreasing the pressure on the low pressure side as well as the evaporator temperature). If in an evaporator the specified value for the temperature is different, the respective control module activates the shut-off valve so that no more refrigerant flows through the evaporator which is too cold. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information) and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
Shut-Off Valve, which is Regulated via the Characteristic Curve
- The shut-off valve -A- is activated via a step motor -B- from the respective control module via the characteristic curve (opened or closed).
- If the shut-off valve works as a regulator valve (for example, on the Audi Q7 as Refrigerant Expansion Valve 1 -N636-), it is opened just enough so that the temperature for the heater core is reached. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information.
- Shut-off valves activated by stepper motors do not have a specified resting position. Therefore they must be set to a certain position (open or closed) before performing work on the refrigerant circuit. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).
- Depending on the refrigerant circuit design, multiple shut-off valves may be combined in one valve block (for example, on the e-Golf or Audi Q7 e-tron). Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).
- The stepper motor is adapted and activated via the data wires (LIN Bus) by the respective control module according to its component location. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function. Refer to Air Conditioning (1 Of 3) / Air Conditioning (3 Of 3) (vehicle-specific Service Information).