I purchased a used Ranco heater valve complete with functioning bellows/capillary tube. The problem is that the temperature adjustment cam/off latch will not "grab" the spring tensioner screw. It is a pressed on, knurled fit that has been stripped. So, I am going to attempt a repair (not sure how right now), but my main question is how was the spring/cam adjusted when new.
The cam will only turn about 7/8 of a turn from "off" to warmest setting. The spring tension adjustment screw has much more travel. I noticed in Denny's photos of his heater valve that the spring looks compressed about half way through it travel in the warmest setting. If this is the case, then the spring is never relaxed when the valve is off and the latch in the off position would have a much harder time "grabbing" the pin/boss.
Here are Denny's photos. Hope you dont mind me using your photos
In the photos you can see the cam in the warmest position hitting the pin/boss that stops its travel. you can also see the spring cap plate halfway in the slot keeping it in position...this represents half its travel from rest or significantly more than one turn of the adjusting screw/cam.
After studying the Ranco valve, I can understand why they continue to function with a broken bellows. The bellows job is to override the spring and close the valve if the temperature climbs too high, thereby providing some sense of automated control. Without the bellows, the driver/passenger has to maintain temperature control by turning the temperature knob.
