Skoda Workshop Service and Repair Manuals

Specified values High-pressure side: From the output pressure (when connecting the pressure gauge) rising up to maximum 20 bar overpressure. Low-pressure side:

From the output pressure (when connecting the pressure gauge) dropping to diagram value. A -  High pressure in bar overpressure. B -  Low pressure in bar overpressure. C -  Permissible tolerance range.

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure remains constant or increases only slightly (above the pressure while engine is not running), l  Low pressure drops quickly to diagram value or lower, l  the required cooling capacity is not reached.	Too little refrigerant in the circuit or expansion valve defective.	–  Drain the refrigerant from the refrigerant circuit. l  The volume of refrigerant suctioned out corresponds approximately to the specified filling capacity: –  Replace expansion valve. –  Newly filling the refrigerant circuit. –  Repeat check. l  The volume of refrigerant suctioned out is considerably less than the specified filling capacity: –  Search for leaks with the leak detector, eliminate. –  Newly filling the refrigerant circuit. –  Repeat check.
l  High pressure is normal, l  Low pressure corresponds to the diagram value, l  the required cooling capacity is not reached.

If no fault is found for this complaint, clean the refrigerant circuit → Chapter.

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure increases above the specified value, l  Low pressure drops quickly to diagram value or lower, l  the required cooling capacity is not reached.	t  Constriction or blockage in the refrigerant circuit. t  Expansion valve defective.	–  Feel the temperature gradient of the refrigerant circuit with the hand. l  A temperature gradient is noticed on a component: –  In case a hose line or a pipe is bent or constricted, replace this component. –  In case of a blockage, clean refrigerant circuit → Chapter, if necessary replace the expansion valve. l  If no fault is found: –  Clean refrigerant circuit → Chapter, if necessary replace the expansion valve. –  Repeat check.

If the function is not in order after cleaning the refrigerant circuit, the expansion valve must be replaced.

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure and low pressure is normal at first, l  after a certain period of time the high pressure rises above the specified value if the low pressure drops to diagram value or lower, l  the required cooling capacity is no longer reached.	t  Expansion valve defective. t  Humidity in the refrigerant circuit.	–  Replace the fluid reservoir or only the dessicator (specifically designed for vehicles) and evacuate the refrigerant circuit for at least 3 hours (see notes). –  Check expansion valve for dirt or corrosion, replace if necessary. –  Clean the refrigerant circuit → Chapter.
l  High pressure and low pressure is normal at first. l  After a longer operating time, the low pressure drops remarkably low (evaporator ices up).

t

If problems arise due to humidity in the refrigerant circuit, only after a longer operating time or only occasionally (the low pressure drops below the specified value and the evaporator ices up), it is adequate to replace the dessicator (the volume of refrigerant oil must be adapted). Subsequently the refrigerant circuit must be evacuated for at least 3 hours.

t

First of all, it is not required to clean the refrigerant circuit for this complaint (to flush with refrigerant R134a or to blow through with compressed air and nitrogen), as normally only a small amount of humidity is present in the system which can be removed through a longer period of evacuation.

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure is normal or too high, l  Low pressure is too high (see diagram), l  the required cooling capacity is not reached, l  the AC compressor makes noises (especially after switching it on).	t  Too much refrigerant in the circuit. t  Expansion valve or AC compressor defective.	–  Drain the refrigerant from the refrigerant circuit. l  The volume of refrigerant suctioned out corresponds approximately to the specified filling capacity: –  Replace expansion valve. –  Newly filling the refrigerant circuit. –  Repeat check. l  The volume of refrigerant suctioned out is considerably more than the specified filling capacity: –  Newly filling the refrigerant circuit. –  Repeat check.

If the function of the air conditioning system is not O.K. when repeating the test, reexchange expansion valve and clean refrigerant circuit → Chapter. Subsequently replace AC compressor and fluid reservoir with dessicator or only dessicator (specifically designed for vehicles).

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure increases only slightly above the pressure while engine is not running, l  Low pressure drops only slightly, l  the required cooling capacity is not reached.	AC compressor defective.	–  Clean the refrigerant circuit → Chapter. –  Replace AC compressor and fluid reservoir with dessicator or only dessicator (specifically designed for vehicles).

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure is normal, l  Low pressure is too low (see diagram), l  the required cooling capacity is reached.	Expansion valve or AC compressor defective.	–  Replace expansion valve. –  Newly filling the refrigerant circuit. –  Repeat check.

t	If the function of the air conditioning system is not O.K. when repeating the test, reexchange expansion valve and clean refrigerant circuit → Chapter. Subsequently replace AC compressor and fluid reservoir with dessicator or only dessicator (specifically designed for vehicles).

t	If this fault occurs, it can happen that the evaporator ices up although the volume of refrigerant in the circuit is O.K.

Possible deviation from the specified value	Possible cause of fault	Rectifying fault
l  High pressure and low pressure is normal, l  the required cooling capacity is not reached.	Too much refrigerant oil in the circuit.	–  Drain refrigerant circuit. –  Clean the refrigerant circuit → Chapter.
l  High pressure and low pressure is normal, l  the AC compressor makes noises (especially after switching it on), l  the required cooling capacity is reached.		–  Newly filling the refrigerant circuit.

t	Over-filling with refrigerant oil can occur if, for example, the AC compressor was replaced without adapting the volume of refrigerant oil.

t

In case too much refrigerant oil is present in the refrigerant circuit, the AC compressor must be emptied and the fluid reservoir with the dessicator or only the dessicator (specifically designed for vehicles) must be replaced. After the refrigerant circuit was cleaned → Chapter, fill the correct volume of refrigerant oil into the circuit.