Information And Tools Required

This Service Information only outlines the checking procedure. Perform the detailed test for this heater function as described in the Guided Fault Finding. Refer to Vehicle Diagnostic Tester in the"Guided Fault Finding"  function.

With the Start/Stop System, the stop function is disabled depending on the setting on the A/C Control Module -J301- (for example, the heater is on). As soon as there is a request for heating, the engine is started. In cooling mode, the A/C Control Module -J301- does not limit the stop function. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding"  function.

If there is no Humidity Sensor -G355- installed on vehicles with a A/C Control Module -J301-, a permissible stop time is currently calculated by characteristics curves which are influenced by the measured outside air temperature, the "recirculated-air mode" function and operating status of the windshield wipers. The calculated time must be greater than 20 seconds so that the stop function is permitted by the A/C Control Module -J301-. The stop time can be shortened at a lower outside air temperature, when recirculated-air mode is active and/or when raining to prevent the front and door windows from fogging up. In the event the calculated time for the stop function is less than 20 seconds, this is prevented.

With the Start/Stop Function, the stop function is disabled depending on the setting on the Climatronic Control Module -J255- control head. If, for example, "Defrost" is selected, the stop function is not possible or will be interrupted and the engine will start. The same applies in the case of heating and cooling. The difference between the target and actual temperature is greater than a specified value. Use the :Vehicle Diagnostic Tester  in the"Guided Fault Finding"  function.