SEAT Workshop Service and Repair Manuals

Specified values High-pressure side: Increasing by a maximum of 20 bar from the initial pressure (when connecting the manometers). Low pressure:

Decreasing to the value of the diagram from the initial pressure (when connecting the manometers). A -  Low-pressure (measured at the service port) in bar absolute pressure. B -  Control current for air conditioner compressor regulating valve -N280- in amps C -  Permissible tolerance range (valid for compressor operation percentage between 10 ... 90 %)   Note t  Under unfavourable conditions (very high ambient temperatures, high air humidity), the pressure in the high-pressure side may increase up 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 according to the control current for the air-conditioner compressor regulating valve -N280- within the tolerance margin in the compressor power range. t  Under unfavourable conditions (very high ambient temperatures, high air humidity), the power may not always be sufficient to reach the prescribed value. t  The set 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 „maximum cooling power“ setting, the control current is set to between approximately 0.65 A and 0.8 A (depending on the vehicle, it is indicated in the measurement value 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. In general, most manometer scales represent atmospheric pressure as 0 bar, meaning an absolute pressure of 1 bar (this can be recognized if there is a -1 on the scale).

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High pressure remains constant or increases only slightly (above the pressure measured when the engine is stopped), l  The low pressure falls to the diagram value or lower, l  Required cooling output is not attained	t  The control for the AC compressor regulating valve -N280- is defective. t  Insufficient refrigerant in circuit. t  Expansion valve defective.	–  Check control for AC compressor regulating valve -N280-. –  Extract some refrigerant from the refrigerant circuit. l  If quantity of refrigerant extracted is substantially less than specified capacity:
l  High pressure is normal, l  Low pressure matches the diagram value, l  Required cooling output is not attained	l  Insufficient 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.	l  –  Renew the expansion valve. –  Recharge refrigerant circuit. –  Repeat the check.

t	Clean the refrigerant circuit (rinse with refrigerant R134a or sweep with compressed air or nitrogen).

t	Check the measured values of the evaporator output temperature sender -G263- and the actuation of the air conditioner compressor regulating valve -N280-. If measured value of evaporator output temperature sender -G263- is not OK, evaporator may ice up or cooling output may not be attained.

t	If, after replacing the expansion valve, operation of the air conditioning system is not OK when the test is repeated (re-fit old expansion valve), clean refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen ). Replace the compressor and liquid tank.

t	When this fault occurs, it is possible for the evaporator to ice up even when the proper quantity of refrigerant is present in the circuit.

t

If the expansion valve is faulty (constantly closed or does not open enough), the air-conditioner compressor regulating valve -N280- is activated at maximum power, and the low pressure drops to or below the value of the diagram (the air-conditioner compressor sucks refrigerant from the low-pressure side). But, as the refrigerant cannot flow through the expansion valve, the cooling power cannot be achieved, and the pressure may also not increase or only increase slightly, seeing as there is no energy transformation.

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High pressure increases only slightly above the pressure measured when the engine is stopped, l  Low pressure falls only slightly, l  Required cooling output is not attained	t  The control for the AC compressor regulating valve -N280- is defective.	–  Check actuation of air conditioner compressor regulating valve -N280-
	t  The air conditioner compressor is defective.	–  Extract refrigerant. –  Flush the refrigerant circuit (clean) –  Renew the air conditioner compressor. –  Recharge refrigerant circuit.

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High pressure rises above specification, l  Low pressure quickly drops to value in graph l  Required cooling output is not attained	t  The control for the AC compressor regulating valve -N280- is defective. t  Restriction or obstruction in the refrigerant circuit. t  Expansion valve defective.	–  Check actuation of air conditioner compressor regulating valve -N280- –  Feel AC circuit with hand to determine temperature differences. l  If temperature differences are perceptible on a component: –  Renew hose or pipe if kinked or constricted. –  In the event of clogging of the refrigerant circuit, clean (flush with refrigerant R134a or blow out with compressed air and nitrogen ). –  Recharge refrigerant circuit. –  Repeat the check. l  If no fault is found. –  Clean refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen ). –  Recharge refrigerant circuit. –  If function is not OK, repeat test: –  Renew the expansion valve and receiver.

t	If this fault occurs, the evaporator may freeze in spite of the fact there is the correct amount of refrigerant in the circuit.

t

If the expansion valve is faulty (constantly closed or does not open enough), the air-conditioner compressor regulating valve -N280- is activated at maximum power, and the low pressure drops to or below the value of the diagram (the air-conditioner compressor sucks refrigerant from the low-pressure side). But, as the refrigerant cannot flow through the expansion valve, the cooling power cannot be achieved, and the pressure may also not increase or only increase slightly, seeing as there is no energy transformation.

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High and low pressure normal at first l  The high pressure increases beyond the specified value, l  The low pressure falls to the diagram value or lower, l  Required cooling output is not attained	t  The control for the AC compressor regulating valve -N280- is defective. t  Moisture in the refrigerant circuit.	–  Check actuation of air conditioner compressor regulating valve -N280- –  Clean refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen ).
l  High and low pressure normal at first l  After lengthy driving time, low pressure drops below specification (evaporator ices up)		–  Renew receiver with dryer. –  Evacuate refrigerant circuit for at least 3 hours. –  Recharge refrigerant circuit. –  Flush the refrigerant circuit (clean) –  Repeat the check.

t

If this incident occurs only after a prolonged service period or occasionally (the low pressure drops to below the specification and the evaporator freezes), only the desiccant needs to be replaced (located in the liquid tank). The amount of refrigerant oil must be compensated for. The refrigerant circuit must now be vacuumed for at least 3 hours.

t	In principle it is not necessary to blow out the refrigerant circuit with compressed air and nitrogen in the event of this complaint, seeing as there is generally only a small amount of humidity in the system which may be eliminated by vacuuming the circuit for a prolonged period of time.

t	If this fault occurs, the evaporator may freeze in spite of the fact there is the correct amount of refrigerant in the circuit.

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High pressure normal, low pressure too low (see diagram), the required cooling power is delivered.	t  The control for the AC compressor regulating valve -N280- is defective. t  Expansion valve or compressor faulty. t  Compressor defective	–  Check actuation of air conditioner compressor regulating valve -N280- –  Clean refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen ) (not always necessary, refer to notes). –  Renew the expansion valve and receiver. –  Recharge refrigerant circuit. –  If function is not OK, repeat test: –  Renew compressor. –  Recharge refrigerant circuit. –  Repeat the check.

t	In the case of the fault „High pressure normal, low pressure too low“, the following must be taken into account: Error, the evaporator may freeze, or the cooling power is not achieved.

t	If this fault occurs, the evaporator may freeze in spite of the fact there is the correct amount of refrigerant in the circuit.

t

Check the measurement value of the evaporator outlet temperature sender -G263- or the evaporator temperature sender -G308- and the controlling of the air conditioning system compressor regulating valve -N280-. If the value measured by the high-pressure sender -G65- is incorrect, the evaporator may freeze or the cooling power is not achieved.

t

If the air-conditioner compressor regulating valve -N280- is faulty (the regulating valve is not activated, but the compressor operates correctly), it is not necessary to blow out the refrigerant circuit. In this case, replacing the air-conditioner compressor is sufficient (compensate for the amount of refrigerant oil in the new air-conditioner compressor).

t

If the expansion valve is faulty (constantly closed or does not open enough), the air-conditioner compressor regulating valve -N280- is activated at maximum power, and the low pressure drops to or below the value of the diagram (the air-conditioner compressor sucks refrigerant from the low-pressure side). But, as the refrigerant cannot flow through the expansion valve, the cooling power cannot be achieved, and the pressure may also not increase or only increase slightly, seeing as there is no energy transformation.

→ Rep. gr.87

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High pressure normal or too high, l  Low pressure too high (see diagram), l  Compressor noise (particularly after switch-on) l  Required cooling output is attained	t  The control for the AC compressor regulating valve -N280- is defective. t  Too much refrigerant in circuit. t  Expansion valve defective. t  Compressor defective	–  Check actuation of air conditioner compressor regulating valve -N280- –  Extract some refrigerant from the refrigerant circuit. l  If quantity of refrigerant extracted roughly corresponds to actual capacity: –  Renew the expansion valve and receiver. –  Recharge refrigerant circuit. –  If function is not OK, repeat test: –  Renew compressor. l  The quantity of refrigerant extracted is significantly greater than the prescribed charge quantity: –  Recharge refrigerant circuit. –  Repeat the check.

t

If the air-conditioner compressor regulating valve -N280- is faulty (the regulating valve is not activated, but the compressor operates correctly), it is not necessary to blow out the refrigerant circuit. In this case, replacing the air-conditioner compressor is sufficient (compensate for the amount of refrigerant oil in the new air-conditioner compressor).

t	The refrigerant circuit may be overcharged with refrigerant oil if, for example, the compressor has been replaced without compensating the amount of refrigerant oil.

t

If the air conditioner compressor is not replaced, the refrigerant must be extracted from the compressor (replace the O-ring) via the oil drain plug. Fill the 50 grams in the → Repair Manual of the respective vehicle indicated complete refrigerant oil quantity in the air conditioner compressor and the rest in the refrigerant circuit.

t

If the expansion valve is faulty (constantly closed or does not open enough), the air-conditioner compressor regulating valve -N280- is activated at maximum power, and the low pressure drops to or below the value of the diagram (the air-conditioner compressor sucks refrigerant from the low-pressure side). But, as the refrigerant cannot flow through the expansion valve, the cooling power cannot be achieved, and the pressure may also not increase or only increase slightly, seeing as there is no energy transformation.

Possible deviation from specification	Possible cause of fault	Measures to be taken
l  High and low pressure normal l  Required cooling output is attained	t  The control for the AC compressor regulating valve -N280- is defective. t  Too much refrigerant in circuit. t  Expansion valve defective.	–  Check actuation of air conditioner compressor regulating valve -N280- –  Drain refrigerant circuit. –  Clean refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen ).
l  High and low pressure normal l  Compressor noise (particularly after switch-on) l  Required cooling output is attained		–  Add correct quantity of refrigerant oil to circuit (see note). –  Recharge refrigerant circuit. –  If function is not OK, repeat test: –  Renew the expansion valve. –  Recharge refrigerant circuit. –  Repeat the check.

t	Overfilling with refrigerant oil may occur if, for example, the compressor has been renewed without adjusting the quantity of refrigerant oil.

t	If expansion valve is defective (permanently open), evaporator temperature is no longer regulated such that only refrigerant in gas form 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).

t	If there is too much refrigerant oil in the circuit, discharge compressor and renew receiver. After cleaning the refrigerant circuit (flush with refrigerant R134a or blow out with compressed air and nitrogen), add the correct amount of refrigerant oil to the circuit → Chapter.