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Home >> Volkswagen >> 2023 >> Tiguan SE R-Line Black, AWD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> General, Technical Data Refrigerant R134A General Information >> 00 General, Technical Data >> Pressures, Checking >> Checking With Expansion Valve And Receiver/Dryer, With Internally Regulated A/C Compressor >> Specified Values
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Specified Values

High-Pressure Side:

Increasing from initial pressure (when connecting the pressure gauges) to a maximum of 20 bar (290 psi).

Low-Pressure Side:

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

Fig 1: Identifying Permissible Tolerance Range Graph
GWWA87-0146Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

A -  High pressure in bar

B -  Low pressure in bar

C -  Permissible tolerance range

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
  • The requested cooling output is not attained.
  • High pressure normal
  • Low pressure in line with value in graph
  • The requested cooling output is not attained.
 Not enough refrigerant in circuit or expansion valve malfunctioning. -- Extract refrigerant from the refrigerant circuit
  • If quantity of refrigerant extracted roughly corresponds to specified capacity:
-- Replace the expansion valve.-- Charge the refrigerant circuit.-- Repeat the test.
  • If quantity of refrigerant extracted is substantially less than specified capacity:
-- Localize the leak with leak detector and eliminate-- Charge the refrigerant circuit.-- Repeat the test.
NOTE:

If no malfunction can be found and the function of the A/C system is not correct after repeating the test, flush (clean) refrigerant circuit with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT . If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with nitrogen. Refer to REFRIGERANT CIRCUIT, CLEANING WITH COMPRESSED AIR AND NITROGEN .

Possible Deviation from Specification Possible Cause of Fault Corrective Action
  • High pressure increases above specification
  • Low pressure quickly drops to value in graph or below
  • The requested cooling output is not attained.
  • Constriction or obstruction in refrigerant circuit
  • Expansion valve malfunctioning
 -- 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.-- If there is an obstruction, flush refrigerant circuit with compressed air and nitrogen and replace expansion valve.
  • If no malfunction can be found.
-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Repeat the test.
NOTE:

If the function is not correct after flushing the refrigerant circuit, the expansion valve must be replaced.

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 and low pressure drops to value in graph or below
  • Required cooling output is no longer attained.
  • Expansion valve faulty
  • Moisture in refrigerant circuit
 -- Examine expansion valve for dirt or corrosion; replace if necessary.-- Flush refrigerant circuit with compressed air and nitrogen.-- Replace receiver/dryer.-- Repeat test if function is not OK.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Charge the refrigerant circuit.-- Repeat the test.
NOTE:

Always replace receiver/dryer in case of this malfunction.

Possible Deviation from Specification Possible Cause of Fault Corrective Action
  • High pressure normal or too high (see diagram),
  • Required cooling output is not attained
  • A/C compressor noise (particularly after switch-on)
  • Too much refrigerant in the circuit.
  • Expansion valve or A/C compressor faulty.
 -- Extract refrigerant from the refrigerant circuit
  • If quantity of refrigerant extracted roughly corresponds to specified capacity:
-- Replace expansion valve-- Charge the refrigerant circuit.-- Repeat test
  • If quantity of refrigerant extracted is substantially greater than specified capacity:
-- Charge the refrigerant circuit.-- Repeat the test.
NOTE:

If the function of the A/C system is not correct when the test is repeated, re-install old expansion valve and flush refrigerant circuit with compressed air and nitrogen. Then replace A/C compressor and receiver/dryer.

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
  • A/C compressor faulty.
 -- Flushing the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .-- Replace the A/C compressor and receiver/dryer.
Possible Deviation from Specification Possible Cause of Fault Corrective Action
  • High pressure normal
  • Low pressure too low (see graph)
  • The required cooling performance is obtained
  • Expansion valve or A/C compressor faulty
 -- Replace expansion valve-- Charge the refrigerant circuit.-- Repeat the test.
NOTE:

If A/C system function is not OK when the test is repeated, flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT . Then replace A/C compressor and receiver/dryer.

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
  • Required cooling output is not attained
 Too much refrigerant oil in the circuit. -- Discharge the refrigerant circuit.-- Flush (clean) refrigerant circuit. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .
  • High and low pressure normal
  • A/C compressor noise (particularly after switch-on)
  • The required cooling performance is obtained
    
NOTE:

Overfilling with refrigerant oil can occur if, for example, the A/C compressor was 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 block connections. 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 the Vehicle-Specific Service Information.

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