So, i've been doing a bit more digging those heater control valves. Apparently they are PWM controlled, meaning that they are not just open/close solenoid, but vary (using variable voltage) the degree to which they are closed (they are normally open) to control the heat in the car. EDIT: I'm reading conflicting information, some say when 12v constant is applied the valve will fully close.
So, i'm not sure they are really suitable. That said, i'm not sure of any alternatives. I bought some cheap solenoid valves for my hot water system (but only have cold running through them) which I was thinking about using. They are pretty flimsy bits of kit though so have some reservations.
I've done some schematics and thinking, and from what I can see, the minimum amount of valves required to get the following modes operation is 3 (single):
- Eber heating van only
- Eber heating engine only
- Engine heating van
I'll try and put something more concrete together as soon as I have it figured.
Edit: this is what i have used inside, only good up to 95 degrees though:
http://www.ebay.co.uk/itm/Electric-...ial_Automation_Control_ET&hash=item231c71a4d8