I have a 1979 w123 with a leaking automatic climate control (ACC)unit. A few years ago I replaced the original one with a rebuilt and now it is leaking. I don't want to spend the money on another one...the car isn't worth it.

I am planning to replace the ACC with a 3/4 ball valve or gate valve set up, bypassing the ACC altogether. I only need one setting for winter (open) and one for summer (closed). Does anyone know if the ACC unit can be subsituted for 1 valve, or are 2 necessary? Is it OK to just turn off the coolant flow to the heater core, or is it necessary to circulate the engine coolant back to the engine when the heater core is valved off?

Any ideas?