Test Step 4

Test Step 4

Control motors of the A/C system and associated potentiometers

• The resistance value of the potentiometers in the control motors (target value: 3.6... 5.7 kohms between contact "1" and "3") can only be measured directly at the control motor (parallel connection).

• The resistance value of the potentiometers in the control motors (between contacts "1" and "2 " and "3" and " 2") depends on the position of the control motor. It can only be measured for an installed control motor. The upper target value is not reached in test steps "4.1" and "4.2". (To reach the upper target value, all connections would have to be disconnected from the other control motors during the measurement in a parallel connection).

• If the fault "potentiometer short circuit to ground" or " open circuit/short circuit to positive" is detected by the Climatronic control module (J255) A/C control head, all potentiometers in the control motors and the associated wire routing must be checked.

• If several control motors are simultaneously displayed as faulty in the DTC memory but no fault can be identified in test step "4", check the potentiometers in all control motors and the wire connections between the individual control motors for short circuit (e.g. between the defroster flap motor (V107) and the central air flap motor (V70); with the connectors disconnected from all control motors and the Climatronic control module ( J255) A/C control head, the measuring device must display " infinite ohms" between jacks "1","2", and " 3" in the associated connector).

• The back pressure flap motor (V71) is only installed in vehicles with steering on the left; it actuates the back pressure/fresh air flap.

• The back pressure flap motor (V71) is not installed in vehicles with steering on the right. In these vehicles the resistance to jack "27" must be infinite ohms (ohms). The fresh air flap is moved in these vehicles by the recirculation flap motor (V113).

• In vehicles with steering on the right, the assignment of the contacts in the connectors is transposed according to the different installation position of the control motors (contact "1" with "3" and " 5" with "6")

• The back pressure flap motor (V71) is only installed in vehicles with steering on the left; it actuates the back pressure/fresh air flap.

• The back pressure flap motor (V71) is not installed in vehicles with steering on the right. In these vehicles the resistance to jack 27 must be infinite ohms∼ (ohms). The fresh air flap is moved in these vehicles by the recirculation flap motor (V113 ).

• In vehicles with steering on the right, the assignment of the contacts in the connectors is transposed according to the different installation position of the control motors (contact "1" with "3" and " 5" with "6")

* Ground applied to connector "D", terminal "13".

• The back pressure flap motor (V71) is only installed in vehicles with steering on the left; it actuates the back pressure/fresh air flap.

• The back pressure flap motor (V71) is not installed in vehicles with steering on the right. The fresh air flap is moved in these vehicles by the recirculation flap motor (V113 ).

• In vehicles with steering on the right, the assignment of the contacts in the connectors is transposed according to the different installation position of the control motors (contact "1" with "3" and " 5" with "6")

• The back pressure flap motor (V71) is only installed in vehicles with steering on the left; it actuates the back pressure/fresh air flap.

• The back pressure flap motor (V71) is not installed in vehicles with steering on the right. The fresh air flap is moved in these vehicles by the recirculation flap motor (V113 ).

• In vehicles with steering on the right, the assignment of the contacts in the connectors is transposed according to the different installation position of the control motors (contact "1" with "3" and " 5" with "6")

• The back pressure flap motor (V71) is not installed in vehicles with steering on the right. In these vehicles the resistance between jacks "49" and "50" must be infinite ohms∼ (ohms).

* Ground applied to connector "D", terminal "13".