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

Volkswagen Polo Service & Repair Manual / Refrrigerant R134a Servicing / Pressures, Checking / Checking with Expansion Valve, Receiver/Dryer and A/C Compressor Regulator Valve -N280-, Externally Regulated A/C Compressor

Specified Values

Note

Connecting service station. Refer to → Chapter „Connecting Service Station“.

Observe test requirements. Refer to → Chapter „Pressures, Checking“.

–	Bring engine speed up to 2000 RPM.

–	Pay attention to the A/C service station pressure gauge.

Note

Switching pressures for actuation of A/C Compressor Regulator Valve -N280- and Coolant Fan -V7- are vehicle-specific.

The pressures should be measured at the service connections. The location of these connections is vehicle-specific. Refer to → Rep. Gr.87.

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.

A -	Low pressure (measured at service connection) in bar (psi) absolute

B -	Control current for A/C Compressor Regulator Valve -N280-.

C -	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. Refer to → Rep. Gr.87.

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). Refer to → Rep. Gr.87.

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).

Checking with Expansion Valve, Receiver/Dryer and A/C Compressor Regulator Valve -N280-, Externally Regulated A/C Compressor

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure remains constant or increases only slightly (above pressure with engine stopped).

Low pressure quickly drops to value in graph or below.

Required cooling output is not attained

Activation of A/C Compressor Regulator Valve -N280- is faulty.

Not enough refrigerant in refrigerant circuit

–	Check activation of A/C Compressor Regulator Valve -N280-.

–	Localize the leak with leak detector and eliminate

–	Charge the refrigerant circuit.

High pressure normal.

Low pressure in line with value in graph.

Required cooling output is not attained

High pressure normal.

Low pressure too low (see graph).

Required cooling output is not attained

Not enough refrigerant in refrigerant circuit

–	Extract refrigerant from the refrigerant circuit

If quantity of refrigerant extracted is substantially less than specified capacity.

–	Localize leak with leak detector and eliminate.

–	Charge the refrigerant circuit.

–	Repeat the test.

If quantity of refrigerant extracted roughly corresponds to specified capacity:

Expansion valve faulty

–	Replace expansion valve

–	Charge the refrigerant circuit.

–	Repeat the test.

Note

If no malfunction is found with this complaint, flush (clean) refrigerant circuit with refrigerant R134a. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“. If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with nitrogen. Refer to → Chapter „Refrigerant Circuit, Flushing with Compressed Air and 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.

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure only increases slightly above pressure with engine stopped.

Low pressure drops only slightly.

Required cooling output is not attained

Activation of A/C Compressor Regulator Valve -N280- is faulty.

–	Check activation of A/C Compressor Regulator Valve -N280-.

A/C compressor faulty.

–	Extract refrigerant circuit.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Replace A/C compressor.

–	Charge the refrigerant circuit.

High pressure increases above specification.

Low pressure quickly drops to value in graph or below.

Required cooling output is not attained

Activation of A/C Compressor Regulator Valve -N280- is faulty.

–	Check activation of A/C Compressor Regulator Valve -N280-.

Constriction or obstruction in refrigerant circuit

–	Run hand over refrigerant circuit to check for differences in temperature

If difference in temperature is found at one component:

–	Replace the hose or pipe if kinked or constricted.

–	In the event of an obstruction, flush refrigerant circuit with compressed air and nitrogen

–	Charge the refrigerant circuit.

–	Repeat the test.

If no malfunction can be found:

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Charge the refrigerant circuit.

–	Repeat test if function is not OK.

Expansion valve faulty

–	Extract refrigerant circuit.

–	Replace expansion valve and receiver/dryer

–	Charge the refrigerant circuit.

Note

With this malfunction, evaporator may ice up although quantity of refrigerant in circuit is OK.

Possible deviation from specification

Possible cause of fault

Corrective action

High and low pressure normal at first, after some time high pressure increases above specification.

after some time, low pressure decreases to graph value or lower.

Required cooling output is no longer attained.

Activation of A/C Compressor Regulator Valve -N280- is faulty.

–	Check activation of A/C Compressor Regulator Valve -N280-.

High pressure and lower pressure normal first, after a long period of driving, the low pressure falls below the specified value (evaporator iced up).

Moisture in refrigerant circuit

–	Extract refrigerant circuit.

–	Flush refrigerant circuit with compressed air and nitrogen.

–	Replace receiver/dryer with dryer.

–	Evacuate refrigerant circuit for at least 3 hours.

–	Charge the refrigerant circuit.

–	Repeat test, if function is not OK.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Charge the refrigerant circuit.

–	Repeat the test.

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.

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure normal, low pressure too low (see graph), the necessary cooling output is not reached.

Activation of A/C Compressor Regulator Valve -N280- is faulty.

–	Check activation of A/C Compressor Regulator Valve -N280-.

Expansion valve faulty

–	Extract refrigerant circuit.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Replace expansion valve and receiver/dryer

–	Charge the refrigerant circuit.

–	Repeat test if function is not OK.

–	Replace the A/C compressor.

A/C compressor faulty.

–	Extract refrigerant circuit.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Replace the A/C compressor.

–	Charge the refrigerant circuit.

–	Repeat the test.

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).

Refer to → Rep. Gr.87.

Possible deviation from specification

Possible cause of fault

Corrective action

High pressure normal or too high.

Low pressure too high (see graph).

A/C compressor noise (particularly after switch-on).

Required cooling output is not attained

Activation of A/C Compressor Regulator Valve -N280- is faulty.

Too much refrigerant in the circuit.

–	Check activation of A/C Compressor Regulator Valve -N280-.

–	Extract refrigerant from the refrigerant circuit

If quantity of refrigerant extracted roughly corresponds to specified capacity:

–	Replace the A/C compressor.

If quantity of refrigerant extracted is substantially greater than specified capacity:

–	Charge the refrigerant circuit.

–	Repeat the test.

To much refrigerant oil in the circuit.

–	Discharge the refrigerant circuit.

If quantity of refrigerant extracted roughly corresponds to specified capacity:

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Charge the refrigerant circuit.

–	Repeat the test.

Expansion valve faulty

–	Discharge the refrigerant circuit.

–	Replace expansion valve and receiver/dryer

–	Charge the refrigerant circuit.

–	Repeat test if function is not OK.

–	Replace the A/C compressor.

A/C compressor faulty.

–	Discharge the refrigerant circuit.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Replace the A/C compressor.

If quantity of refrigerant extracted is substantially greater than specified capacity:

–	Charge the refrigerant circuit.

–	Repeat the test.

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.

Possible deviation from specification

Possible cause of fault

Corrective action

High and low pressure normal.

Required cooling output is not attained

Activation of A/C Compressor Regulator Valve -N280- is faulty.

To much refrigerant oil in the circuit.

–	Check activation of A/C Compressor Regulator Valve -N280-.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

High and low pressure normal.

A/C compressor noise (particularly after switch-on).

The required cooling performance is obtained

To much refrigerant oil in the circuit.

–	Discharge the refrigerant circuit.

–	Flush (clean) refrigerant circuit. Refer to → Chapter „Refrigerant Circuit, Flushing (Cleaning) with Refrigerant R134a“.

–	Charge the refrigerant circuit.

–	Repeat the test.

Expansion valve faulty

–	Replace expansion valve

Note

Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil.

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.

Checking with Restrictor, Reservoir and A/C Compressor Regulator Valve -N280-, Externally Regulated A/C Compressor

Note Connecting service station. Refer to → Chapter „Connecting Service Station“. Observe test requirements ...

Components, Replacing

...

Other materials:

A/C Compressor Regulator Valve -N280
Note For switching pressures, removing and installing switches and switch arrangement and version, see vehicle-specific refrigerant circuit. Refer to → Rep. Gr.87. ...

Using a child seat on the front passenger seat
Fig. 63 On the sun visor on the passenger side: airbag sticker First read and observe the introductory information and safety warnings Not all countries allow you to transport children on the front passenger seat. Not every child seat is suitable for use on the front passenger seat. Volkswa ...

Cleaning windows and exterior mirrors
First read and observe the introductory information and safety warningsCleaning windows and exterior mirrors Moisten the windows and exterior mirrors with commercially available, alcohol-based glass cleaner. Dry the glass surfaces with a clean chamois leather or a lint-free cloth. Chamois l ...