300D Heat always on....

[rwthomas1]

Hello All,
Got a new problem with my '84 300D. The heat is always on, no matter what position the ACC controls are in. About two weeks ago I drove away from the house and the heat just never turned off. It always ran a bit since the garage is quite cool before switching to AC but now full heat all the time.

-I have replaced the ACC (pushbutton control) with a new unit from GDL
-Monovalve removed, bench tested, seems to function normally, opens and closes repeatedly and seals when blown through. Was rebuilt a few years back.
-No voltage present on the Monovalve control wire with ACC temp wheel at 72 and the heat kicking.
-Visually checked fuses, all seems in order.

What next? The car is undriveable as it is.

Thanks, RT