Cooling Output, Checking
Test requirements are met, refer to TEST REQUIREMENTS
-- Measure the ambient temperature (it must higher than 15 °C).
-- Close doors, hood, windows and sun roof.
-- Open all instrument panel vents.
-- Switch ignition on.
-- Start the engine.
-- Switch on Econ on the Climatronic control module (the indicator lap in the ECON button will come on; the indicator lamp in the AC button will not come on).
-- Initiate a Guided Fault Finding on the A/C system using Vehicle Diagnosis, Testing and Information System VAS 5051.
-- In read measured values block select the display group with the measured values for the compressor control and refrigerant circuit pressure and read the measured values using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
- The A/C compressor is switched off, a current of 0 A (amps) will be displayed.
- The pressure in the refrigerant circuit is same as the measured outside temperature or greater than the value in the chart.
| Ambient temperature in °C | Pressure display (in bar absolute) |
|---|---|
| 15 | 4, 7 |
| 20 | 5, 6 |
| 25 | 6, 6 |
| 30 | 7, 6 |
| 35 | 8, 8 |
- In terms of absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure equals approximately 1 bar absolute pressure. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (can be seen from -1 mark below 0).
- Depending on version of Climatronic control module, only integer values may be displayed in the measuring value block, if the pressure measured lies between two values the display switches back and forth.
- Pressure in refrigerant circuit is governed by ambient temperature. On account of heat given off by components (e.g. radiator), pressure displayed with warm engine will be slightly higher than that given for the respective ambient temperature.
If the displayed pressure in the refrigerant circuit is lower than in the table:
- Check signal of High Pressure Sensor -G65-, refer to HIGH PRESSURE SENSOR, CHECKING PRESSURE SIGNAL .
- If no malfunction can be detected at High Pressure Sensor, there is insufficient refrigerant in the circuit, bring vehicle to a workshop that has the necessary tools and in which the work can be performed accordingly by qualified personnel, refer to A/C PRESSURE/TEMPERATURE SENSOR -G395- .
If pressure in refrigerant circuit is OK (the same or greater than specified in the table)
-- Switch on A/C compressor, select operating mode "Auto" on Climatronic control module to do so.
-- Set temperature preselect for driver and front passenger side to Lo on Climatronic control module.
-- Set direction of air flow to instrument panel vents at the Climatronic control module.
-- Read the required values in Guided Fault Finding using Vehicle Diagnosis, Testing and Information System VAS 5051.
Check the following values:
- The A/C compressor is on and a duty cycle greater than 30% is being displayed (the A/C Compressor Regulator Valve -N280- is working).
- The A/C compressor is one and a current greater than 03 Amps is displayed (the current is flowing through the A/C compressor regulator valve).
- The displayed pressure increases above the value when the compressor is switched off.
- If the displayed pressure does not change and the A/C compressor is working correctly, then make sure one more time that the A/C compressor is actually being driven. If the A/C compressor is being driven, there is a malfunction in the refrigerant circuit. Bring vehicle to a workshop that has the necessary tools and in which the work can be performed accordingly by qualified personnel, refer to REFRIGERANT CIRCUIT CONCERNS and refer to PRESSURES, CHECKING and refer to REMOVAL AND INSTALLATION . (it is possible that A/C compressor regulation is not OK). Bring the problems determined to the attention of the workshop.
- The A/C compressor regulator valve is controlled by the Climatronic control module so that the air temperature reaches the specified value (approximately 2 to 5 °C) after the evaporator:
- After starting the engine, and depending on the measured temperature, the engine RPM and voltage for controlling the A/C compressor regulator valve, a value greater than 75% (0.55 amps) is displayed. As soon as the temperature measured by Evaporator Vent Temperature Sensor -G263- nears the specified value, the activation, and thus the compressor output, is reduced.
- Under certain operating conditions, moisture in the refrigerant circuit can lead to ice build-up on the A/C compressor regulator valve (and on the expansion valve). A/C compressor control is reduced by this ice build-up, evaporator is cooled too intensely and freezes. The ice on the evaporator may cause various customer concerns, refer to ICE FORMATION ON EVAPORATOR, LOCALIZING MALFUNCTION .
- If no current or very little current is displayed in the A/C compressor regulator valve measured values block, then check the A/C compressor regulator valve, refer to A/C COMPRESSOR REGULATOR VALVE, CHECKING SWITCH-ON SIGNAL .
-- Press button for recirculating air mode on Climatronic control module (symbol for recirculating air mode lights up in button).
-- Set engine speed of 2000 rpm (start of time measurement).
-- In "read measured values block", select the display with the measured value from the evaporator vent temperature sensor. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
-- Compare the displayed measured value (of the evaporator vent temperature sensor) to the values in the diagram using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
A - Measured air temperature of Evaporator Vent Temperature Sensor
B - Ambient temperature
C - Permissible tolerance range
Depending on the ambient temperature, the measured air temperature should be after 5 minutes within the shown tolerance range.
- If the required values are not reached, check the measured values on the evaporator vent temperature sensor, on the Left Vent Temperature Sensor -G150- and on the Right Vent Temperature Sensor -G151-, then compare the displayed measured values with each other:
- If the measured value deviates in the display fields, then perform the procedure for identifying malfunctions if specified values are not reached. Refer to DETERMINING MALFUNCTION IF SPECIFIED VALUES ARE NOT OBTAINED .
- If measured value of evaporator vent temperature sensor is greater than measured value of Left Vent Temperature Sensor and Right Vent Temperature Sensor, check evaporator vent temperature sensor for proper installation and perform an electrical test for this sensor, refer to Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function.
- The function of the air conditioning is recognizable, e.g. the refrigerant pipe on the low pressure side (thick line) cools off.
If the measured value for the evaporator vent temperature sensor (and therefore the system output) is OK:
-- Compare the measured value for the evaporator vent temperature sensor with the measured values for the left vent temperature sensor and right vent temperature sensor.
The left vent temperature sensor and right vent temperature sensor measured values may not be greater than maximum 3 °C after 5 minutes, than the evaporator vent temperature sensor measured value.
If the required values are not reached, then compare the displayed measured values from the left vent temperature sensor and the right vent temperature sensor to each other:
- If the measured value in one of the two sensors is OK, then check the activation and function of the left Temperature Door Motor -V158- and the Right Temperature Door Motor -V159-, refer to TEMPERATURE INCREASE DOWNSTREAM FROM EVAPORATOR, DETERMINING MALFUNCTION , HEATING PERFORMANCE OF A/C SYSTEM, CHECKING and Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
- If the measured value from the left vent temperature sensor and from the right vent temperature sensor is lower then the value from the evaporator vent temperature sensor make sure the evaporator vent temperature sensor, left vent temperature sensor and right vent temperature sensor are installed correctly and check their electrical connectors for contact resistance. Replace the faulty sensor if necessary. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
- If there is no malfunction on the left vent temperature sensor and the right vent temperature sensor as well as on the left temperature door motor and the right temperature door motor, then determine the malfunction with temperature increase downstream of the evaporator. Refer to TEMPERATURE INCREASE DOWNSTREAM FROM EVAPORATOR, DETERMINING MALFUNCTION .
- A commercially available thermometer can also be used to measure the air temperature coming out of the center instrument panel vents.
- If there are different air temperatures coming out of the vents, then this may be caused by the following: the temperature doors in the air distribution housing are not closing completely or they are not reaching their end position, refer to AIR GUIDE IN EVAPORATOR HOUSING and Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding", there is air inside the heat exchanger (the air is not flowing evenly through the heat exchanger and therefore is not being warmed evenly, refer to) HEATING PERFORMANCE OF A/C SYSTEM, CHECKING or the foam seal came loose when installing the heat exchanger and the air is flowing over the heat exchanger.