I think funola just did an alligator clip to lock down the monovalve and then fixed his ground-to-pin 4 trace to stop the "all-heat-all-the-time" syndrome.

The monovalve gets +12v from the fuse box and the CCU provides the ground path to close it. ID the hot pin and the ground pin and see if you can get to close in positions other than "O". If so, check your traces in the CCU or research funola's thread.

Monovalve which fuse?