Defrost Function Test

WARNING: This page is about a different car, the 2001 Mercedes-Benz SL500 and 2000 Mercedes-Benz SL500. However, it is still accessible from the selected car via links, so may be relevant.

Press defrost button. Allow temperature to stay at random setting. If operation is correct, fan speed will increase, air will vent from defrost outlets, A/C compressor will engage, there will be maximum heat output, and inlet air will be 100 percent fresh air. If this mode does not operate properly, perform the following tests:

DTC B1232: REFRIGERANT PRESSURE SENSOR under DIAGNOSTIC TESTS.
DTC B1422: SERIAL INTERFACE (K1) under DIAGNOSTIC TESTS.
DTC B1416: COOLANT CIRCULATION PUMP under DIAGNOSTIC TESTS.
DTC B1417: AUTOMATIC A/C MONOVALVE under DIAGNOSTIC TESTS.
BLOWER REGULATOR CONTROL in MISCELLANEOUS ELECTRICAL TESTS under SYSTEM TESTS.
DTC B1419: A/C COMPRESSOR CLUTCH under DIAGNOSTIC TESTS.
DTC B1423: SWITCHOVER VALVE BLOCK under DIAGNOSTIC TESTS.