Alex Crow
Senior Member
- Joined
- Jul 9, 2009
- Messages
- 10,677
- Reaction score
- 47
- Location
- Super Suffolk
- Your Mercedes
- W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
...I'm figuring that depending on the setting of the heat knob, the controller puts a voltage on the other leg of the solenoid. The potential difference between the two legs is what regulates the position of the valve and in turn the water flow...
Pretty much, but it does not regulate the voltage, but switch an earth, giving the 0v.
When it is open circuit no current will flow and PD = 0v
When the circuit to earth is made current can flow, and PD = (circa) 12v
The water flow temperature is regulated by switching the valves on and off at a low frequency, but the valves are essentially supposed to be either fully open or closed.
Hence open vs closed time will control flow temps.
One other test you could try is switching the outer pins around in the plug, if the cold side of the car swaps over, that takes you to the control panel, without passing 'GO'.