Car is a 1975 240D. The left "red" heater control just moves back and forth and seems to be "broken". The right hand one works or seems to have some resitance, but no heat at all can be found in car. Fan blows fine.

The "three way valve on firewall engine side appears to have two wires connected to it. Can this three way valve (with heater hoses connected) be my cause. Do they foul or get stuck?

Let me know if it is a DIY fix and how long can it take.

Regards Tom