We have a 2001 Alpine 34' FDDS. The heater is made by ACME (yes, Wiley Coyote!) and has an electric-servo-operated "H" valve. Last summer we noticed it was still producing heat on the vent setting with the temperature control at minimum. So I obtained a replacement "H" valve from Acme and installed it. The valve is held in place by an "L" bracket mounted to the back wall of the generator compartment The front part of the L bracket is attached to the servo body by #6 sheet metal screws (1/4" hex head). As received from Acme, those screws are used to hold the servo to the "H" valve via a formed metal bracket, and they're just the right length for the servo-and-formed-bracket thickness. There is no spare length for another bracket.
Well, guess what - the installers at WRV used those screws anyway.
I believe the non-turnoff problem was caused simply by the screws eventually pulling loose, so that the servo separated from the "H" valve and the little shaft connecting the two slipped out of its connecting slot on the servo.
So, before paying $100-plus for the valve assembly from Acme, try substituting 3/4-inch #6 screws for the originals! You'll probably have to fiddle some with the relative positions of the valve shaft and the servo socket.
Franklin & Dessa
2001 Alpine 34 FDDS
Tow a 2014 CR-V