Volkswagen Tiguan Service and Repair Manual: Checking with Expansion Valve, Receiver/Dryer and A/C Compressor Regulator Valve -N280-, Externally Regulated A/C Compressor

Specified Values

Note

• Connecting service station.
• Observe test requirements.

• Bring engine speed up to 2000 RPM.
• Pay attention to the A/C service station pressure gauge.

Note

High-pressure side:

Increasing from initial pressure (when connecting pressure gauges) to 20 bar (290 psi).

Low-pressure side:

Decreasing from initial pressure (when connecting pressure gauges) to the value in the graph.

1. Low pressure (measured at service connection) in bar (psi) absolute
2. Control current for A/C Compressor Regulator Valve -N280-.
3. Permissible tolerance range

Note

• Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar (421 psi).
• The control current -B- is shown in the measured value block.
• The high pressure measured from the High Pressure Sensor -G65- is not shown in the measured value block.
• Low pressure settles as a function of control current for A/C Compressor Regulator Valve -N280- within compressor output range in tolerance range.
• Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value.
• The specified operating current for the regulator valve must be greater than 0.3 A in order to ensure reliable valve activation.
• In the setting "maximum cooling output" control current is regulated to approximately 0.65 A up to 0.8 A (vehicle specific, displayed in measured value block).
• At absolute pressure, 0 bar/psi corresponds to absolute vacuum. Normal ambient pressure corresponds to 1 bar (14.5 psi) absolute pressure. 0 bar/psi pressure corresponds to an absolute pressure of 1 bar (14.5 psi) on most pressure gauges (indicated by 1 bar (14.5 psi) below 0 bar/psi).

Note

• If no malfunction is found with this complaint, flush (clean) refrigerant circuit with refrigerant R134a. If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with nitrogen.
• Check measured values from Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308- and activation of A/C Compressor Regulator Valve -N280-. If the measured value of the Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308- is not OK, the evaporator can ice up or the cooling output will not be reached.
• If the function of the air conditioning system is not OK when the test is repeated after replacing expansion valve, re-install old expansion valve and flush refrigerant circuit with compressed air and nitrogen. Then replace A/C compressor and receiver/dryer.
• With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.
• If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve -N280- is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Because refrigerant cannot flow through the expansion valve, the correct cooling output cannot be reached. The high pressure may not increase or may only increase slightly.

Note

• With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.
• If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve -N280- is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Because refrigerant cannot flow through the expansion valve, the correct cooling output cannot be reached. The high pressure may not increase or may only increase slightly.

Note

• If this complaint occurs after a long operating time or only sporadically (the low pressure falls under the specified value and the evaporator ices up), replacing the dryer (installed in the receiver/dryer) is sufficient. The quantity of refrigerant oil should be adjusted. Refrigerant circuit is then to be evacuated for at least 3 hours.
• First, it is not necessary to flush the refrigerant circuit with compressed air and nitrogen in case of this complaint because generally only a small amount of moisture is in the system and this can be removed by a long evacuation.
• With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.

Note

• For the malfunction "high pressure normal, low pressure too low", note the following: faulty, the evaporator can ice up or the cooling output is not reached.
• With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.
• Check measured values from Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308- and activation of A/C Compressor Regulator Valve -N280-. If the measured value of the High Pressure Sensor -G65- is faulty, the evaporator can ice up or the cooling output is not reached.
• If the problem is with the A/C Compressor Regulator Valve -N280- (regulating valve is not actuated but compressor operates nevertheless), refrigerant circuit does not have to be flushed. With this malfunction, replacing the A/C compressor is sufficient (adjust refrigerant oil quantity in new A/C compressor).
• If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve -N280- is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Because refrigerant cannot flow through the expansion valve, the correct cooling output cannot be reached. The high pressure may not increase or may only increase slightly.

Note

• If the problem is with the A/C Compressor Regulator Valve -N280- (regulating valve is not actuated but compressor operates nevertheless), refrigerant circuit does not have to be flushed. With this malfunction, replacing the A/C compressor is sufficient (adjust refrigerant oil quantity in new A/C compressor).
• Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
• If the A/C compressor is not replaced, the refrigerant oil should be drained from the A/C compressor via the oil drain plug. Out of the entire quantity of refrigerant oil, 50 grams should be put in the A/C compressor and the rest in the refrigerant circuit. Refer to vehicle-specific repair manual.
• If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve -N280- is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). Because refrigerant cannot flow through the expansion valve, the correct cooling output cannot be reached. The high pressure may not increase or may only increase slightly.

Note

• Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.
• If the A/C compressor is not replaced, the refrigerant oil should be drained from the A/C compressor via the oil drain plug. Out of the entire quantity of refrigerant oil, 50 grams should be put in the A/C compressor and the rest in the refrigerant circuit. Refer to vehicle-specific repair manual.
• If expansion valve is malfunctioning (permanently open), evaporator temperature is no longer regulated such that only refrigerant in gaseous state exits from the evaporator. Under certain usage conditions, liquid droplets may then be drawn in by the compressor and cause noise (liquid cannot be compressed).

With Expansion Valve, Receiver/Dryer and Electrically-Driven A/C Compressor

Note

The electrically-driven A/C compressor does not have an A/C Compressor Regulator Valve -N280-. The A/C compressor RPM does the regulating. The A/C compressor contains the control electronics and a G-charger, which moves the refrigerant.