We recently bought a Defiant Encore 0028 that was rarely used and is in near mint condition. Installed it and it generally works great. But, the primary air seems to be stuck halfway open so no matter what we do, we get a fire about 600 and can't damp it down. Great for colder days, but not really very versatile. I can pull the door shut in the back by grabbing the cable tag end , put it just pops back to half open and doesn' t respond to the temperature adjustment lever at all. Any suggestions?