Defrost Mode
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2001 Mercedes-Benz ML55, 2001 Mercedes-Benz ML430, 2001 Mercedes-Benz ML320, 2000 Mercedes-Benz ML55, and 2000 Mercedes-Benz ML430. However, it is still accessible from the selected car via links, so may be relevant.
To check operation in defrost mode, set temperature selector knob to White range (vertical). Set mode control knob to 12-o'clock position (vertical). Ensure A/C button indicator is illuminated. Air will vent from defrost and center outlets and A/C compressor will engage. If operation is not as specified, perform the following in order:
- Check voltage supply circuit Z50/2 between No. 16 fuse (15-amp) and connected components. See VOLTAGE SUPPLY CIRCUIT Z50/2 under ELECTRICAL TESTS.
- Check ground circuit. See GROUND CIRCUIT Z50/4 under ELECTRICAL TESTS.
- Check in-vehicle temperature sensor signal voltage. See IN-VEHICLE TEMPERATURE SENSOR under ELECTRICAL TESTS.
- Check in-vehicle temperature sensor signal resistance. See IN-VEHICLE TEMPERATURE SENSOR under ELECTRICAL TESTS.
- Check icing protection temperature sensor signal voltage. See ICING PROTECTION TEMPERATURE SENSOR under ELECTRICAL TESTS.
- Check icing protection temperature sensor resistance. See ICING PROTECTION TEMPERATURE SENSOR under ELECTRICAL TESTS.
- Check activation voltage during temperature reduction. See ACTIVATION VOLTAGE TEMPERATURE under ELECTRICAL TESTS.
- Check activation voltage during temperature increase. See ACTIVATION VOLTAGE TEMPERATURE under ELECTRICAL TESTS.
- Check blend air flap actuator motor operation voltage. See BLEND AIR FLAP ACTUATOR MOTOR under ELECTRICAL TESTS.
- Check blend air flap actuator motor resistance. See BLEND AIR FLAP ACTUATOR MOTOR under ELECTRICAL TESTS.
- Check A/C button activation. See A/C BUTTON under ELECTRICAL TESTS.
- Check A/C pressure switch. See A/C REFRIGERANT PRESSURE SWITCH under ELECTRICAL TESTS.