Just turned stove on for first time this season. Every thing was fine until the distribution blower came on, an alarm like sound comes from stove. When auger motor stops the noise stops. When auger is running without dist. blower on no noise. When everything is running I can turn blower speed way down and noise goes away. Stove is 13 years old. Distribution blower was replaced 3 years ago, combustion blower replaced last year. Any ideas before I call service guy?