VW Tiguan Manuals

Volkswagen Tiguan Service and Repair Manual: Checking with Expansion Valve and Receiver/Dryer, with Internally Regulated A/C Compressor

Volkswagen Tiguan Service and Repair Manual / Refrigerant R134a Servicing / Pressures, Checking / Checking with Expansion Valve and Receiver/Dryer, with Internally Regulated A/C Compressor

Note

  • Connecting service station.
  • Observe test requirements.

 

  • Bring engine speed up to 2000 RPM.
  • Observe manometer battery.

Note

Switching pressures and design of refrigerant circuit switches are vehicle-specific.

The pressures should be measured at the service connections. The location of these connections is vehicle-specific.

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.

  1. High pressure in bar (psi)
  2. Low pressure in bar (psi)
  3. Permissible tolerance range

Volswagen Tiguan. A87-0146

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
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 expansion valve
  • Charge the refrigerant circuit.
  • Repeat the test.
  • High pressure normal
  • Low pressure in line with value in graph
  • Required cooling output is not attained
 
  • 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. If that is not possible in this workshop, flush the refrigerant circuit with compressed air and remove moisture with 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
  • Required cooling output is not attained
  • Constriction or obstruction in refrigerant circuit
  • Expansion valve faulty
  • 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.
  • 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.
  • 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.
  • Flush (clean) refrigerant circuit.
  • Replace 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. 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
To much refrigerant oil in the circuit.
  • Discharge the refrigerant circuit.
  • Flush (clean) refrigerant circuit.
  • 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 in the event, 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.

Checking with Expansion Valve and Receiver/Dryer, without Regulated A/C Compressor

Test Requirements

  • Radiator and condenser are clean (clean if necessary).
  • The ribbed belt for the A/C compressor and alternator tensioned correctly.
  • All air ducts, covers and seals are OK and installed correctly.
  • The doors reach their end position.
  • The engine is warm.
  • Evaporator and heater not drawing in secondary air (at maximum fresh-air blower speed).

With engine running and A/C system set to maximum cooling output, pay attention to the following points:

  • The fresh air blower is running.
  • The coolant fan must be running or it must be switched on.
  • The recirculation/fresh air door must be in the "recirculation" position.
  • Ambient temperature is greater than 15 0C.
  • The A/C Evaporator Temperature Switch -E33- is installed correctly and its switch temperatures are correct.

Checking

  • Turn off the ignition.
  • Connect pressure gauge battery (A/C service station).
  • Take pressure gauge readings. There are two possible results A and B.
Ambient Temperature in ºC (ºF) Pressure in Refrigerant Circuit in Bar (psi) Positive Pressure
15 (60) 3.9 (57)
20 (68) 4.7 (68)
30 (86) 6.7 (97)
40 (104) 9.1 (132)

A- The pressure in the refrigerant circuit is lower than the pressure specified in the table. There is not enough refrigerant in the circuit.

  • Search for leak with leak detection device.
  • The pressure release valve is open, check coolant fan activation according to the wiring diagram.

Check refrigerant pipes and hoses to see if they are bent too sharply (cross-section constrictions) or have external damage. If no malfunction is found, flush refrigerant circuit.

B - The pressure in the refrigerant circuit matches the table or is higher.

  • Start the engine.
  • Set A/C system to maximum cooling output.
  • Open doors.
  • Open vents in instrument panel.

The A/C compressor is driven by the engine via the magnetic clutch using the ribbed belt.

Note

  • If the A/C compressor is not driven, check A/C Clutch -N25- voltage supply.
  • If the voltage supply is OK, repair the magnetic clutch.

If the A/C compressor is driven, check refrigerant circuit:

  • Bring engine speed up to 2000 RPM.
  • Observe manometer battery

Specified Values

High-pressure side:

Increasing from pressure with engine not running to a maximum of 20 bar (290 psi).

Low-pressure side:

Decreasing from pressure with engine not running down to 1.3 bar (18.9 psi).

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