Mercedes® OEM Heater Control Mono Valve Solenoid, 1981-1991 (126)

On the later model Mercedes the HVAC heater control valve solenoid and the A/C evaporator and heater core are contained in the same housing. Temperature control is automatic and is controlled by temperature sensors. Once a temperature is selected it is maintained automatically by the temperature control unit repositioned dampers to control air flow through the unit. The temperature control unit determines how to position the dampers by comparing the signals from the sensors. From there it is either directed through the heater core or bypassed the heater core (via a system of flappers) and into the cabin. A faulty HVAC heater control valve solenoid can send false readings resulting in poor heating or cooling of the A/C system.