I'm hoping that my problem is an easy fix but nothing is ever easy. My heater functions normally except that after the blower starts, when the igniter fires the gas off there is a loud woof. There has always been a slight woof sound when it ignites but now it is to the point that it sounds like it has to much gas in the chamber and is on the verge of exploding inside. It still runs "normal" and cycles off and on as it always has. It seems like a valve is leaking gas into the combustion chamber when it is not in the heat mode. Any suggestion? Another thing, is it normal for the burner to cycle off and on about every minute or so?