A/C System Cooling Peformance, Testing
A/C System Cooling Performance, TestingNote:
Under certain operating conditions, residual moisture in refrigerant circuit can lead to an ice build-up at compressor regulator valve. Compressor control is reduced by this ice buildup, evaporator is cooled too intensely and freezes. The freeze-up of the evaporator can be the cause fbr the following customer complaints:
- After a long drive, A'C system repeatedly or sporadically fails (no cooling or heating performance), after switching off vehicle and after a short time, A/C function is OK again.
- After a long drive, windows fog up from inside, windows are also not cleared by pressing the "Defrost" button, after switching off vehicle and after a short time, A/C function is OK again.
Corrective Action:
- For vehicles as of model year 2002 and a compressor with A/C Compressor Regulator Valve -N280-, check measured value of Evaporator Vent Temperature Sensor -G263- "Read measuring value blocks" display group "010". If measured value of the sensor is too low under operating conditions specified by customer (at an ambient temperature above 0°C, colder than 0°C for a long period of time although A/C Compressor Regulator Valve -N280- is not cunently being activated), transfer vehicle to an authorized service shop for A/C systems.
- In vehicles without Evaporator Vent Temperature Sensor -G263- e.g. via Sender for outlet temperature, floor outlet -G192-, check at the adjustment: "Temperature Lo" for driver's- and passenger side, 4 or 5 bars tor fresh air blower RPM, air outlet in footwell and fresh air operation under operating conditions specified by customer. If measured value of the sensor is too low (at an ambient temperature above 0°C, colder than 0°C for a long period of time), transfer vehicle to an authorized service shop for A/C systems.
- Check refrigerant line from evaporator to accumulator (thick tube, low pressure side) with engine running. If this line is thickly iced-up when complaint occurs (a very thin layer of ice is permitted), this indicates that the temperature in evaporator is too low, transfer vehicle to an authorized service shop for A/C systems.
- Bring the determined deficiency to the attention of the authorized service shop for A/C systems, the necessary work can only be performed there (draining refrigerant circuit, replacing accumulator and then evacuating the refrigerant circuit for a minimum of 3 hours).
Test Requirements
- Radiator and condenser clean (clean if necessary)
- Ribbed belt OK and correctly tensioned and drive plate actually drives compressor (6 and 8 cylinder gas engine).
- Compressor drive unit (connection between compressor and engine) is correctly installed (only Audi Aliroad with 4.2 L engine).
- Air flow through dust and pollen filter not obstructed by dirt
- Air conditioner unit properly sealed (when fresh air blower is at maximum speed setting, no additional air is drawn in; air delivery is via vents only)
- Vehicle not standing in direct sunlight
- Engine at normal operating temperature
- All instrument panel vents open.
- Engine running and A/C oontrol head -E87- set as follows:
^ AUTO mode
^ Compressor switched on (LED in ECON button not lit up)
^ Temperature selection LO (for both driver's and passenger's side)
^ Compressor activated (A/C clutch -N25- switched on)
^ A/C Compressor Regulator Valve -N280- is switched on (on vehicles using -N280- Read Measuring Value Block display group 001 and 002).
^ Coolant Fan -V7- running (speed depends on pressure in refrigerant circuit and engine temperature)
^ Fresh Air Blower -V2- running at maximum speed
^ Fresh airirecirculated air flap moved to "recirculated air'1 mode (within 1 minute of starting engine)
^ Air should oome out of the instrument panel vents
^ Both temperature flaps in "cooling" position
Note:
Check DTC memory if one test requirement is not attained and Carry out output Diagnostic Test Mode.
Preparatory steps
- Connect VAG 1551 scan tool and press buttons -0- and -8- to insert AC/Heating Electronics" address word 08 and advance program until "Select function "XX" appears on display.
- Carry out basic setting and check coding.
- Close hood and sunroof
- Measure ambient temperature
- Close doors and windows
Cooling Performance Checking (Vehicles From Model Year 2002)
- Measure ambient temperature (must greater than 15°C).
- Close doors, hood, window and sunroof.
- Open all dash panel vents.
- Switch ignition on.
- Select ECON mode on A/C control head -E87- (indicator light in ECON button lights up).
- Start engine.
- Connect VAG 1551 scan tool and press buttons -0- and -8- to insert AC/Heating Electronics" address word 08 and advance program until "Select function "XX" appears on display.
- Initiate "Read Measuring Value Block" function 08 and select display group "001 "for vehicles from model year 2002.
- Check indication in display fields:
^ Display field "2" shows 0% (compressor is switched off)
^ Display field "4" shows, that the pressure in the refrigerant circuit measured at ambient temperature is the same or greater as the table value.
Note:
- At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure corresponds to approximately 1 bar absolute pressure. 0 pressure corresponds to an absolute pressure of one baron most pressure gauges (indicated by -1 below 0).
- The pressure in the refrigerant circuit depends on the ambient temperature. Via heat emission of oomponents (e.g. coolant fan), with the engine at operating temperature a slightly higher pressure is displayed than the respeetive ambient temperature.
- If the displayed pressure is lower than in the table:
^ Check measuring value of High Pressure Sensor -G65- "Read Measuring Value Block" and "electrical testing, test step 5"
^ Not enough refrigerant in circuit, if no malfunction can be detected on high pressure sensor. Determine and eliminate the cause.
Climate control with refrigerant R134a If the pressure in the refrigerant circuit is OK.
- Switch compressor on, for this select ECON mode on A/C control head -E87- (indicator light in ECON button does not light up).
- Select temperature mode "Lo" (for driver's and passenger's side) on A/C Control Head -E87-.
- Select air flow direction on A/C Control Head - E87- to "air from dash panel vents"
- Select "Read Measuring Value Block" function 08 display group "001".
- Check indication in display fields:
^ A duty cycle greater than 30% is displayed in display field "2" (compressor is switched on, A/C Compressor Regulator Valve -N280- is activated or compressor is being driven via the A/C Clutch -N25-).
^ A current greater than 0.3 A is displayed in display field "1" (current flows via A/C Compressor Regulator Valve -N280-, compressor is switched on) in vehicles with a compressor with A/C Compressor Regulator Valve -N280-.
^ In vehicles with a compressor with A/C Clutch -N25- compressor is driven. A current greater than 0.1 A is displayed in display field "1", depending on version of A/C Control Head - E87- (current flows via A/C Clutch Relay -J44-, compressor is driven via the A/C Clutch -N25-).
^ The shown pressure in display field "4" rises above the value with the compressor switched on.
Notes:
- If display field "1"shows no or too little current on vehicles with A/C Compressor Regulator Valve -N280-, check:
^ A/C Control Head -E87- activates A/C Compressor Regulator Valve -N280- so that the air temperature after evaporator reaches the specified value (approx. 2 to 5 °C). A value greater than 75% (0.55 A) is displayed after vehicle start, depending on measured temperature, engine speed and vehicle electrical supply. As soon as the temperature measured by Evaporator Vent Temperature Sensor -G263- approaches the specified value, the activation is decreased and therefore compressor performance is reduced.
- The activation of A/C Compressor Regulator Valve -N280- "electrical testing, test step 6".
- In vehicles with a compressor with A/C Clutch -N25-, compressor is not being driven, check:
^ The activation of A/C Clutch Relay -J44- "electrical testing, test step 7".
- If the shown pressure in display field "4" does not change and the activation of the compressor is OK (display field "1"and "2"), the refrigerant circuit has a malfunction. Determine and eliminate the cause.
Climate control with refrigerant R134a
- Press button for "air recirculation" (symbol for "air recirculation" mode button is lit up).
- Inorease engine speed to 2000 RPM (timed period begins).
Continuation of test:
Continuation for vehicles with compressor using A/C Compressor Regulator Valve -N280-
- Initiate "Read Measuring Value Block" function 08 and select display group "010" for vehicles from model year 2002.
- Compare displayed measuring value (of Evaporator Vent Temperature Sensor -263-) in display field "1" with values in diagram.
A - Measured air temperature of Evaporator Vent Temperature Sensor -G263-
B - Ambient temperature
C - Permissible tolerance
Depending on the ambient temperature, the measured air temperature should be after 5 minutes within the shown tolerance range.
Notes:
- If the reguired values are not attained, check the measuring value of Evaporator Vent Temperature Sensor -G263-, compare shown measuring values in display group "010" display field "1" and display group "009" display fields "3" and "4" with each other.
- If the measuring value in both display fields "3" or "4" deviates only slightly from the measuring value in display group "010", Carry out "Identifying malfunctions if specified values are not obtained".
- If the measuring value of Evaporator Vent Temperature Sensor -G263- is greater than Left Vent Temperature Sensor -G150- and Right Vent Temperature Sensor -G151-, check -G263- for correct installation and carry out electrical testing for this sensor "Electrical testing, test step 2".
^ The operation of the air conditioning is recognizable, e.g. the refrigerant pipe on the low pressure side (big line) cools off
If the measuring value of Evaporator Vent Temperature Sensor -G263- is OK (and therefore the cooling performanoe of the air conditioning system).
- Compare the measuring value (of Evaporator Vent Temperature Sensor -G263-) in display group "010" display field 1 with the measuring values of display group "009" display fields "3" and "4" (-G150- and -G151-).
After 5 minutes, the measuring values in display group "009" display field "3" and "4" can be maximum 3°C greater than the value in display field "1" of display group "010" (of Evaporator Vent Temperature Sensor -G263-).
Notes:
- If the required values are not obtained, compare displayed measuring values in display group "009" display fields "3" and "4" with each other:
- If the measuring value in one the two display fields "3" or "4" OK. Check positioning motor for temperature flap on the side where the measuring value is not OK (Actuator for temperature flap left -V158- or Actuator for temperature flap right -V159-), "electrical testing, test step 2".
- If the measuring value in display group "009" display fields "3" or "4" lower than the measuring value in display group "010" display field "1", check Evaporator Vent Temperature Sensor -G263-, Left Vent Temperature Sensor -G150- and Right Vent Temperature Sensor -G151- for correct installation and their electrical connections fbr contact resistance, if necessary replace faulry sensor.
- If no maffunction is detected on -G150- and - G151-, as well as on -V158- and -V159-, carry out "Identifying malfunction at temperature raise after evaporator".
^ The air temperature of the center dash panel vents can be measured e.g. using the VAG 1362 mini tester.
^ The measuring value of Sender for outlet temperature, floor outlet -G192- is shown in display group "009" display field "1". This sensor shows an incorrect value, because in AUTO mode most of the air flow is directed to the dash panel vents. By pressing the "Air to footwell" button, this sensor can also be checked in this test.
��Identifying Malfunctions If Specified Values Are Not Obtained:
ٯ�Continuation Of Test - Pressure In Refrigerant Circuit Increases.:
Notes:
- The pressure in the refrigerant circuit depends on various factors. However, at an ambient temperature between 20 to 25°C the pressure should not exceed more than 20 bar. Due to high coolant performance, pressures up to 31 bar may occur under extreme operating conditions (e.g. in southern countries with high ambient temperatures, "stop and go" traffic and high humidity).
- The pressure in the refrigerant system does not increase above 16 bar at ambient temperatures lower than 25°C (the coolant fan runs and cools the condenser).
- Via the duty cycle (Read Measuring Value Block, display group "001" display field "3") the A/C Control Head -E87- calculates the pressure in the refrigerant circuit.
- when the duty cycle is less than 12.5% (corresponds to approx.: 1.8 bar absolute pressure) and greater than 87.5% (corresponds to approx.: 32 bar absolute pressure) the compressor is not switched on by the A/C Control Head -E87- (A/C Compressor Regulator Valve -N280- is not activated). The compressor will be switched on again when duty cycle is greater than 15% (correspond 2.6 bar absolute pressure) or less than 48% (corresponds to 16 bar absolute pressure).
- If the pressure in the refrigerant circuit or the engine coolant temperature is too high, the A/C Control Heed -E87- regulates the compressor pefformance (to avoid sudden compressor cut-off):
- When pressure in refrigerant circuit exceeds 30 bar (absolute pressure) (the complete compressor output is only switched again after the pressure is less than 27 bar).
- As soon as the coolant temperature reaches 115°C (at 118°C compressor is switched completely).
- Additional notes on pressures in the refrigerant circuit "Read Measuring Value Block" display group "001".
Q�Identifying Malfunctions At Temperature Increase Behind Condenser:
Continuation for vehicles with compressor using A/C Clutch -N25-
- Close center dash panel vent (the "left" and "right" dash panel vents stay open)
- Initiate "Read Measuring Value Block" function 08 and select display group "009" for vehicles from model year 2002.
- Compare displayed measuring values (of -G150- and -G151-) in display fields "3" and "4" with values in diagram.
A - The measured air temperature of Left Vent Temperature Sensor -G150- and Right Vent Temperature Sensor -G151-
B - Ambient temperature
C - Permissible tolerance
Depending on the ambient temperature, the measured air temperature should be after 5 minutes within the shown tolerance range.
Notes:
- If the required values are not obtained, compare displayed measuring values in display gmup "009" display fields "3" and "4" with each other:
- If measuring values in display fields "3" or "4" differ only slightly from each other, Carry out "Identifying malfunctions if specified values are not obtained".
- If the measuring value of one sensor is substantially great& than the measuring value of the other sensor:
^ Check Left Vent Temperature Sensor -G150- and Right Vent Temperature Sensor -G151- for correct installation and check sensor electrically "electrical testing, test step 2".
^ Check operation of Actuator for temperature flap left -V158- and Actuator for temperature flap right -V159- and actuator lever.
^ If no malfunction is recognized on -G150- and -G151-, cany out "Identifying maffunction at temperature increase after evaporator".
- The operation of the air conditioning is recognizable, e.g. the refrigerant pipe on the low pressure side (big line) cools off
- The air temperature of the oenter dash panel vents can be measured e.g. using the VAG 1362 mini tester.
- The measuring value of Sender for outlet temperature, floor outlet -G192- is shown in display group "009" display field "I". This sensor shows an inoorvect value, because in AUTO mode most of the air flow is directed to the dash panel vents. By pressing the "Air to Ibotwell" button, this sensor can also be checked in this test.
� �Identifying Malfunctions If Specified Values Are Not Obtained:
�J�Continuation Of Test - Pressure In Refrigerant Circuit Increases:
Notes:
- The pressure in the refrigerant circuit depends on various factors. However, at an ambient temperature between 20 to 25°C the pressure should not exceed more than 20 bar. Due to high coolant performance, pressures up to 31 bar may occur under extreme operating conditions (e.g. in southern countries with high ambient temperatures, "stop and go" traffic and high humidity).
- The pressure in the refrigerant system does not increase above 16 bar at ambient temperatures lower than 25 °C (the coolant fan runs and cools the condenser).
- Via the duty cycle (Read Measuring Value Block, display group "001" display field "3") the A/C Control Head -E87- calculates the pressure in the refrigerant circuit.
- When the duty cycle is less than 12.5% (corresponds to appmx.: 1.8 bar absolute pressure) and greater than 87.5% (corresponds to approx.: 32 bar absolute pressure) the compressor is not switched on by the A/C Control Head -E87- (A/C Compressor Regulator Valve -N280- is not activated). The compressor will be switched on again when duty cycle is greater than 15% (correspond 2.6 bar absolute pressure) or less than 48% (corresponds to 16 bar absolute pressure).
- Additional notes on pressures in the refrigerant circuit "Read Measuring Value Block" display group "001".
;y�Identifying Malfunctions At Temperature Increase Behind Condenser:
