BMW Diagnostic System - FHK (Rear Climate Control System)

Diagnostic System Notes
The following component functions and signals are processed or controlled by the FHK control unit but not stored as a defect code in the case of a fault:
- *Buttons for footwell in the operating unit
- *Blower control voltage to blower motor output stage
- *Activation of A/C relay via FHK relay box
- Diagnostic links RxD/TxD to the BMW Service Tester

*These component functions and signals can be read out in the status lists of the BMW DIAGNOSTIC SYSTEM.

Defect Code Memory
The FHK control unit clears the defect code memory when the voltage supply (terminal 30, terminal 15) is interrupted or the ignition was off for longer than 3 minutes. After switching on the ignition. all defective components or functions are stored as defect codes.

The display "current defect" shows that there is a defect. The component or function is then not used by the control unit. If a "current defect" is indicated for the temperature sensor or control wheels, a substitute value made available by the control unit is used for these components. The control unit makes an exception for the stepper motors as regards defect detection and defect code storage. In this case, a defect is detected only after ignition "ON", whereby the ignition must have been switched off for longer than 3 minutes beforehand or the power supply was interrupted. When the FHK system is in operation (ignition "ON") and a stepper motor defect occurs, this defect is not stored in the form of a defect code.

Abbreviations
A Output
E Input
Max Maximum
AUTO Automatic
(control in accordance with the flap programs stored in the control unit)
Poti Potentiometer
M Ground