SEAT Workshop Service and Repair Manuals

Specifications: High-pressure side: Rising from starting pressure (when manometer is connected) to 20 bar. Low-pressure side:

Falling from starting pressure (when manometer is connected) to diagram value. A -  Low pressure (measured at the service connection) in bar absolute pressure. B -  Control current for A/C compressor regulating valve, air conditioning system -N280-. C -  Permitted tolerance range.   Note! t  Under unfavourable conditions (very high ambient temperatures, high atmospheric humidity), the pressure on the high-pressure side can increase to a maximum of 29 bar. t  The control current -B- is indicated in the measured values block. t  The high-pressure value measured by the high-pressure sender -G65- is indicated in the measured values block → Rep. Gr.87. t  The low pressure is adjusted to within tolerances within the output range for the air conditioner compressor depending on the control current for the A/C compressor regulating valve, air conditioning system -N280-. t  Under unfavourable conditions (very high ambient temperatures, high atmospheric humidity), the output may be insufficient to achieve the specification in every case. t  The specified working current for the regulating valve must be greater than 0.3 A to ensure that the regulating valve is reliably activated. t  At the setting “maximum cooling power”, the control current should be approx. 0.65 A to 0.8 A (vehicle-specific, indicated in the measured values block) → Rep. Gr.87. t  Absolute pressure means that 0 bar corresponds to an absolute vacuum. The normal ambient pressure corresponds to 1 bar absolute pressure. On most manometers, a reading of 0 bar corresponds to an absolute pressure of one bar (which is confirmed by the existence of a -1 bar marking beneath the 0 scale marking).

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure remains constant or increases only slightly (above the pressure measured when the engine is stopped). l  Low pressure falls quickly to the diagram value or lower. l  the required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective. t  Insufficient refrigerant in circuit.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-. –  Look for leaks using leak detector and rectify them. –  Recharge refrigerant circuit.
l  High pressure normal. l  Low pressure matches the diagram value. l  the required cooling power is not delivered.
l  High pressure normal. l  Low pressure too low (see diagram). l  the required cooling power is not delivered.	l  Too little refrigerant in circuit.	–  Extract some refrigerant from the refrigerant circuit. l  The quantity of refrigerant extracted is significantly less than the prescribed charge quantity. –  Look for leaks using leak detector and rectify them. –  Recharge refrigerant circuit. –  Repeat check. l  The quantity of refrigerant extracted is about equal to the prescribed charge quantity.
	l  Expansion valve defective	–  Renew expansion valve. –  Recharge refrigerant circuit. –  Repeat check.

Note! t  If no fault can be found for this complaint, flush refrigerant circuit with compressed air and nitrogen. t  Check the measured values of the evaporator output temperature sender -G263- and actuation of the A/C compressor regulating valve, air conditioning system -N280-. If the measured value at the high pressure sender -G65- is faulty, the evaporator can ice up or the required cooling power is not delivered. t  If a repeat test after the expansion valve has been renewed indicates that the air conditioning system is still not operating correctly, refit the expansion valve and flush the refrigerant circuit with compressed air and nitrogen. Then renew the air conditioner compressor and receiver. t  In this case, the evaporator may ice up although the correct quantity of refrigerant is present in the refrigerant circuit. t  If the expansion valve is defective (always closed or not opening wide enough) the A/C compressor regulating valve, air conditioning system -N280- will be set to maximum power and the low pressure value will fall to the diagram value or less (the A/C compressor extracts refrigerant from the low pressure side). However, since no refrigerant can flow through the expansion valve, the required cooling power is not delivered, and it can be that the high pressure value does not rise at all or not enough, since no energy exchange is occurring.

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure increases only slightly above the pressure measured when the engine is stopped. l  Low pressure falls only slightly. l  the required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-.
	t  The air conditioner compressor is defective.	–  Extract refrigerant. –  Rinse (clean) refrigerant circuit → Chapter. –  Renew air conditioner compressor. –  Recharge refrigerant circuit.
l  High pressure increases beyond the specification. l  Low pressure falls quickly to the diagram value or lower. l  the required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-.
	t  Restriction or obstruction in the refrigerant circuit.	–  Feel the refrigerant circuit with the hand to sense the temperature gradient. l  At one component a temperature gradient will be detected: –  If a hose or pipe is kinked or crushed, renew it. –  In case of an obstruction, flush refrigerant circuit with compressed air and nitrogen. –  Recharge refrigerant circuit. –  Repeat check. l  If no faults are found: –  Rinse (clean) refrigerant circuit → Chapter. –  Recharge refrigerant circuit. –  Repeat the check; if the system does not operate correctly
	t  Expansion valve defective.	–  Extract refrigerant. –  Renew the expansion valve and receiver. –  Recharge refrigerant circuit.

Note! t  In this case, the evaporator may ice up although the correct quantity of refrigerant is present in the refrigerant circuit. t  If the expansion valve is defective (always closed or not opening wide enough) the A/C compressor regulating valve, air conditioning system -N280- will be set to maximum power and the low pressure value will fall to the diagram value or less (the A/C compressor extracts refrigerant from the low pressure side). However, since no refrigerant can flow through the expansion valve, the required cooling power is not delivered, and it can be that the high pressure value does not rise at all or not enough, since no energy exchange is occurring.

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure and low pressure are normal at first, but after a time the high pressure increases beyond the specification. l  after a time, the low pressure falls to the diagram value or lower. l  The required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-.
l  High pressure and low pressure are normal at first, but after a longer drive, the low pressure falls to below the specification (evaporator iced up).	t  Moisture in the refrigerant circuit.	–  Extract refrigerant. –  Flush refrigerant circuit with compressed air and nitrogen. –  Renew receiver together with dryer. –  Evacuate refrigerant circuit for at least 3 hours. –  Recharge refrigerant circuit. –  Repeat the check; if the function is not OK –  Rinse (clean) refrigerant circuit → Chapter. –  Recharge refrigerant circuit. –  Repeat check.

Note! t  If this complaint occurs after a longer period of operation or only occasionally (the low pressure falls below the specification and the evaporator ices up) it is sufficient only to renew the dryer (fitted within the receiver). Check the quantity of refrigerant oil. Then evacuate the refrigerant circuit for at least 3 hours. t  In case of this complaint, it is not initially necessary to flush the refrigerant circuit with compressed air and nitrogen, since as a rule only a small quantity of moisture will have accumulated in the system, which can be removed by a longer evacuation period. t  In this case, the evaporator may ice up although the correct quantity of refrigerant is present in the refrigerant circuit.

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure normal, low pressure too low (see diagram), the required cooling power is delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-.
	t  Expansion valve defective.	–  Extract refrigerant. –  Rinse (clean) refrigerant circuit → Chapter. –  Renew the expansion valve and receiver. –  Recharge refrigerant circuit. –  Repeat the check; if the system does not operate correctly –  Renew the air conditioning system compressor.
	t  The air conditioner compressor is defective.	–  Extract refrigerant. –  Rinse (clean) refrigerant circuit → Chapter. –  Renew the air conditioning system compressor. –  Recharge refrigerant circuit. –  Repeat check.

Note! t  If the fault is “high pressure normal, low pressure too low ” note the following: defective, the evaporator can ice up or the required cooling power is not delivered. t  In this case, the evaporator may ice up although the correct quantity of refrigerant is present in the refrigerant circuit. t  Check the measured values of the evaporator output temperature sender -G263- and actuation of the A/C compressor regulating valve, air conditioning system -N280-. If the measured value at the high pressure sender -G65- is faulty, the evaporator can ice up or the required cooling power is not delivered. t  If the defect is in the A/C compressor regulating valve, air conditioning system -N280- (the regulating valve is not activated but the A/C compressor still runs), it is not necessary to flush the refrigerant circuit. If this fault occurs, it is sufficient to renew the A/C compressor (check the refrigerant oil quantity in the A/C compressor). t  If the expansion valve is defective (always closed or not opening wide enough) the A/C compressor regulating valve, air conditioning system -N280- will be set to maximum power and the low pressure value will fall to the diagram value or less (the A/C compressor extracts refrigerant from the low pressure side). However, since no refrigerant can flow through the expansion valve, the required cooling power is not delivered, and it can be that the high-pressure value does not rise at all or not enough, since no energy exchange is occurring. → Rep. Gr.87

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure normal or too high. l  Low pressure too low (see diagram). l  The air conditioner compressor is noisy (especially immediately after being switched on). l  the required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective. t  Too much refrigerant in circuit.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-. –  Extract some refrigerant from the refrigerant circuit. l  The quantity of refrigerant extracted is about equal to the prescribed charge quantity: –  Renew the air conditioning system compressor. l  The quantity of refrigerant extracted is significantly greater than the prescribed charge quantity: –  Recharge refrigerant circuit. –  Repeat check.
	t  Too much refrigerant in the circuit.	–  Evacuate refrigerant circuit. l  The quantity of refrigerant extracted is about equal to the prescribed charge quantity. –  Rinse (clean) refrigerant circuit → Chapter. –  Recharge refrigerant circuit. –  Repeat check.
	t  Expansion valve defective.	–  Evacuate refrigerant circuit. –  Renew the expansion valve and receiver. –  Recharge refrigerant circuit. –  Repeat the check; if the system does not operate correctly –  Renew the air conditioning system compressor.
	t  The air conditioner compressor is defective.	–  Evacuate refrigerant circuit. –  Rinse (clean) refrigerant circuit → Chapter. –  Renew the air conditioning system compressor. l  The quantity of refrigerant extracted is significantly greater than the prescribed charge quantity. –  Recharge refrigerant circuit. –  Repeat check.

t

If the defect is in the A/C compressor regulating valve, air conditioning system -N280- (the regulating valve is not activated but the A/C compressor still runs), it is not necessary to flush the refrigerant circuit. If this fault occurs, it is sufficient to renew the A/C compressor (check the refrigerant oil quantity in the A/C compressor).

t

If the expansion valve is defective (always closed or not opening wide enough) the A/C compressor regulating valve, air conditioning system -N280- will be set to maximum power and the low pressure value will fall to the diagram value or less (the A/C compressor extracts refrigerant from the low pressure side). However, since no refrigerant can flow through the expansion valve, the required cooling power is not delivered, and it can be that the high-pressure value does not rise at all or not enough, since no energy exchange is occurring.

Possible deviation from specification	Possible cause of fault	Rectifying fault
l  High pressure and low pressure are normal. l  the required cooling power is not delivered.	t  Actuation of A/C compressor regulating valve, air conditioning system -N280- defective. t  Too much refrigerant in the circuit.	–  Check actuation of A/C compressor regulating valve, air conditioning system -N280-. –  Rinse (clean) refrigerant circuit → Chapter.
l  High pressure and low pressure are normal. l  The air conditioner compressor is noisy (especially immediately after being switched on). l  the cooling power called for is delivered.	t  Too much refrigerant in the circuit.	–  Evacuate refrigerant circuit. –  Rinse (clean) refrigerant circuit → Chapter. –  Recharge refrigerant circuit. –  Repeat check.
	t  Expansion valve defective.	–  Renew expansion valve.

t	Overfilling with refrigerant oil can occur if the refrigerant oil level was not checked after the air conditioner compressor was renewed.

t

If the expansion valve is defective (always open) the evaporator temperature will no longer be regulated so that only gaseous refrigerant exits the evaporator. It is then possible that under certain operating conditions, drops of liquid will be drawn into the air conditioner compressor, which will hen cause noise (because liquid is incompressible).