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Function Test

WARNING: This page is about a different car, the 1998 Mercedes-Benz C43, 1998 Mercedes-Benz C280, and 1998 Mercedes-Benz C230. However, it is still accessible from the selected car via links, so may be relevant.
  1. To check defrost, put temperature at a random setting. Press defrost button. If operation is correct, fan speed will increase, air will vent from upper 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, see DTC B1232 , DTC B1422 , and DTC B1417 & B1418  under SELF-DIAGNOSTICS. Also see A/C ELECTRONIC BLOWER REGULATOR CONTROL  and VACUUM CIRCUITS & SWITCHOVER VALVES  .
  2. To check total ventilation in cooling mode, set temperature to LO. Press AUTO button. If this mode is operating properly, fan speed will increase, air will vent from center and side outlets, A/C compressor will engage, and there will no heat output. If this mode does not operate properly, see DTC B1232 , DTC B1417 & B1418 , DTC B1451 , DTC B1452 , DTC B1457 , DTC B1458 , DTC B1453 , and DTC B1454  under SELF-DIAGNOSTICS. Also see VACUUM CIRCUITS & SWITCHOVER VALVES .
  3. To check normal ventilation in regulating mode, put temperature at present in-vehicle temperature. Press AUTO button. If this mode is operating properly, fan speed will decrease, air will vent from upper outlets and leak from lower outlets, A/C compressor will engage, temperature of outlet air will be controlled, and duovalve and coolant pump will cycle. If this mode does not operate properly, see DIAGNOSTIC OUTPUT  or DTC B1232 , DTC B1417 & B1418 , DTC B1451 , DTC B1452 , DTC B1457 , DTC B1458 , DTC B1453 , and DTC B1454  under SELF-DIAGNOSTICS. Also see VACUUM CIRCUITS & SWITCHOVER VALVES .
  4. To check economy operation (not in heating mode), set temperature to LO. Press EC button. Press dash air outlet mode. If this mode is operating properly, air will vent from dash outlets and A/C compressor will be off. If this mode does not operate properly, see DTC B1419  and DTC B1451  under SELF-DIAGNOSTICS. Also see VACUUM CIRCUITS & SWITCHOVER VALVES .
  5. To check economy operation (in heating mode), set temperature to HI. Press EC button. If this mode is operating properly, air will vent from footwell and side outlets, leak from defrost outlets, and maximum heat will be output. If this mode does not operate properly, see A/C ELECTRONIC BLOWER REGULATOR CONTROL  or DTC B1417 & B1418 , DTC B1419 , DTC B1455 , DTC B1451 , DTC B1452 , DTC B1457 , DTC B1458 , DTC B1453 , and DTC B1454  under SELF-DIAGNOSTICS. Also see VACUUM CIRCUITS & SWITCHOVER VALVES .
  6. To check REST mode, turn ignition off. Press REST. Set temperature to 79°F. If this mode is operating properly, heated air will vent from footwell and side outlets, leak from defrost outlets, and blower will operate at low speed. If this mode does not operate properly, see A/C ELECTRONIC BLOWER REGULATOR CONTROL  or DTC B1417 & B1418 , DTC B1419 , DTC B1455 , DTC B1457 , DTC B1458 , and DTC B1453  under SELF-DIAGNOSTICS. Also see VACUUM CIRCUITS & SWITCHOVER VALVES .
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