[Breadfather]

Originally Posted by hatzie

That pretty much narrows it down.

If the light goes out then the metering portion of the combination valve is moving. The proportioning piston may be stuck.
You can disassemble it and try to free up the valve with some denatured alcohol before putting down $70 on a replacement.

The I have disassembled all of that and re assembled I don't see how it could be getting stuck but that doesn't mean that it isn't. The little flare part on the red plastic proportioning piston, what keeps it from seating in on the back side? I think it is seating because there is no pressure on the rear side of the valve, but how to I generate pressure on the rear side to prevent it from seating? Could that big spring be too weak from being tripped for who knows how long? Looking at that diagram, it would seem to me that a vacuum on the rear side of the system would cause the piston to slide back and seat it again preventing flow? Or am I totally misunderstanding the operation of this valve?

Also, where can I get denatured alcohol?