My A/C doesn't get fully cold until Max on the temp wheel is selected -even then it is intermittent (mostly cold though). Any other position from Max I get hot air mixed with the cold air...sometimes alot of hot air. I have a new mono valve (the valve itself, not the exterior housing) and am now curious if the electro magnet in the mono valve assembly is not performing, or whether I am not getting the correct voltage to the electro magnet.

I understand that the electro magnet regulates the mono valve to supply hot water to the heater core when heat is called for. While I had the mono valve apart replacing the valve itself, I had my son go to max on the temp wheel and the electro magnet would only sometimes push the valve closed, other times if I were to pull the valve, the magnet would hold it. As soon as he came off of Max, the valve would go to the default hot position.

Since it defaults to hot, that the voltage required when hot air is called for, I am assuming the voltage would be 0. I am also assuming that full cold would be 12 volts to the electro magnet within the mono valve assembly, and other temperatures would be somewhere between 0 volts and 12 volts, depending on the amount of heat or cold called for.

I have several questions in order to trouble shoot this properly.
First: Am I assuming the voltage values correctly?
Secondly: What supplies voltage to the mono valve assembly? Does it come directly from the climate control, or is there something between the climate control and the mono valve itself (perhaps an amplifier or such)?

The A/C itself is working properly and is charged with freon. The issue here is one of the mono valve letting hot water through the heater core and ultimately in to the cabin.

Any trouble shooting advice would be helpful!

1983 300D Turbo 190,000 miles
Thanks in advance!