Volkswagen Tiguan Service and Repair Manual: 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.
- High pressure in bar (psi)
- Low pressure in bar (psi)
- 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
- 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
|
|
- 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).
Note
Connecting service station
Observe test requirements
Bring engine speed up to 2000 RPM.
Pay attention to the A/C service station pressure gauge.
Note
Switching pressures for refr ...
Note
Connecting service station.
Observe test requirements.
Bring engine speed up to 2000 RPM.
Pay attention to the A/C service station pressure gauge.
Note
Switching pressures for actu ...