Safety Concept

The safety concept is intended to inhibit any system malfunction, particularly unintentional control operations, through monitoring of signals and function relevant parameters. If faults are detected, the system is switched over or shut down depending on the affected component. The driver is informed of existing faults via the display. Detected faults are stored for diagnostic purposes.

In order to ensure high system availability, existing faults, as far as possible, are cleared with terminal 15 ON. This is done by resetting the fault counter to zero. However, the fault memory content in the EEPROM is retained and can be read out for diagnostic purposes. The system is then operational again. The fast troubleshooting helps to detect existing faults before control operation can take place.

Only lowering is permitted if:

• The permissible supply voltage of 9 volts is undershot
• The permissible compressor running time of 480 seconds is exceeded.

A reset takes place if the voltage is in the OK range of 9 to 16 volts or after the compressor pause time of 100 seconds has elapsed.

Only raising is permitted if:

• The permissible control down period of 40 seconds is exceeded
• The reset takes place the next time the vehicle is driven or after the next control up operation.

No control operation takes place if:

• The permissible supply voltage of 16 volts is exceeded

The reset takes place as soon as the voltage is in the OK range.