I lost heat last week for no apparent reason. I replaced the monovalve and it works, and I am getting vacuum from the whit line from the servo, but apparently the other white line that t's in near the servo isn't holding the vacuum. I can manually open the monovalve and still have no heat. The only thing I have changed in the last week is i had to take the AC belt off and haven't replaced it, but I can't see why that would matter. Any ideas??

Please post model and year of vehicle.

sorry. thought it was on my signature. 1980 300d

__________________
1980 300d on veggie

Is the aux. water pump working?
To eliminate any remaining doubts about the monovalve, disconnect the lead to it...no power to it = full heat.

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

I had a monovalve default to the closed position rather than the open position. When connected it also pushed down to close the valve when it shouls have gone up. I replaced the monovalve and it works fine.

I just replaced the monovalve, and I hooked up the auxilliary water pump directly and it works fine.

__________________
1980 300d on veggie