The service manual says this about the monovalve: "The monovalve is a magnetic valve controlled by electronic switching unit for temperature control in a 5 second cycle. The valve is powered directly from the fuse box and grounded by the electronic switching unit for temperature control depending on deviation from actual and desired temperature. If ground is connected, the [valve] is completely closed."

What does that mean? Could the monovalve be controlled with a manually operated reostat? In other words, will the valve modulate from full closed at 12 volts to full open at zero volts?