I have a Sta-Rite NA400 Natural Gas. This is it's 5th season. Last year in September 2009 the heater started to turn off after 30-45 seconds. It would ignite, heat, and shut down. Control board AFS light is lit. Also there is one flashing light in the Control Box grey panel. I replaced the AFS switch and the Thermal Regulator. Also replaced the wiring harness since most wires were chewed from mice and I had spliced them. The exhaust is blowing warm and fairly forceful. Sta-Rite tech support said that it sounds like a blower whci as you know is an expensive part to try out. Any ideas would be appreciated.