E 300 (124.131) L6-3.0L DSL (606.910) (1995)
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Heater Control Valve: Description and Operation
Monovalve
PURPOSE
The mono valve controls the coolant flow through the heat exchanger (heater core).
LOCATION
The mono valve is located in the return circuit of the heat exchanger, near the battery.
Mono Valve
OPERATION
The mono valve receives power directly from the fuse box and ground from the ACC control unit. The valve is open when ground is not present and
closed when ground is present.
Opening and closing times are activated by the ACC control unit for temperature control and dependent on the deviation from actual and desired
temperature. Ground is applied in 5-second cycles.
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Increased frequency of ground to the mono valve will cause less coolant to flow through the heat exchanger, producing a lower temperature.
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If ground is not present, the valve will be open continuously, providing the heat exchanger with coolant and producing a higher temperature. In the
event of a power failure, the mono valve will remain open (fail safe).
The check valve (arrow) in the lower housing section of the mono valve prevents the heat exchanger from being filled with coolant when the engine is
stopped.
