I have a Armstrong Ultra sx80 model #S8400C30919 natural gas furnace. It has the third Honeywell contol valve SV9502H2522 smart valve. Every time that the valve is replaced, it works flawlessly for 6 months. When it does noy work here is the sequence. Thermostat calls for heat, the blower starts for clearing excess gas, done! It just runs until I shut off the thermostat and try again. Same! All three times that the valve was replace it worked. Any suggestions would help. Next step is a new furnace!