Determining Malfunction if Specified Values Are Not Obtained

Determining Malfunction if Specified Values Are Not Obtained

The required cooling output is not reached during the cooling output test. Refer to => [ Cooling Output, Checking ] Cooling Output, Checking.






Continuation of test: "Pressure in refrigerant circuit increases"






• The pressure in the refrigerant circuit depends on several factors. However, in general, the pressure should not exceed 20 bar at an ambient temperature of 20 to 25 °C. Pressures up to 31 bar may occur due to extremely high performance under severe conditions (such as in southern countries with a hot climate, "stop and go" traffic and high humidity).

• At ambient temperatures below 25 °C, pressure in refrigerant circuit does not normally exceed 16 bar (coolant fans run and cool condenser).

• The Climatronic control module (J255) calculates the refrigerant circuit pressure using the duty cycle signal from the high pressure sensor (G65) (display in the measured values block). At a duty cycle less than 10% (corresponds to approximately 1.2 bar absolute pressure) and greater than 78% (corresponds to approximately 32 bar absolute pressure), Climatronic control module does not switch on the compressor ( A/C Compressor Regulator Valve (N280) is not activated). The A/C compressor is only switched on again after duty cycle has become greater than 12% (corresponds to 1.8 bar absolute pressure) or less than 74% (corresponds to 29 bar absolute pressure).

• If the pressure in the refrigerant circuit or the engine coolant temperature is too high, Climatronic control module regulates the A/C compressor performance (to avoid sudden A/C compressor cut-off). As soon as pressure in refrigerant circuit exceeds 30 bar (absolute pressure), full compressor performance is only enabled again after pressure has become less than 27 bar, or coolant temperature exceeds 115 °C (it is switched off completely at 118 °C ).

• If the pressure in the refrigerant circuit was greater than 32 bar (duty cycle greater than 78%) the A/C compressor is switched on again by the Climatronic control module, if pressure drops below 29 bar (duty cycle is less than 74%).

• Additional information on pressure in the refrigerant circuit can be found in => [ High Pressure Sensor (G65), Checking Pressure Signal ] High Pressure Sensor (G65), Checking Pressure Signal and (VAS5051B) in "Guided Fault Finding."