Need help our furnace comes on for a second then shuts off, comes on and shuts off. Any ideas before I call the furnace man. It's a high efficiency furnace.

A common problem in a high efficiency gas furnace (80% efficient or better) that will cause those exact symptoms is an obstruction in the exhaust flue. Since the exhaust is forced with a small blower, there is a pressure switch on the flue that shuts off the furnace if the pressure in the flue gets too high.

Check for birds nests, dead birds or mice, or other possible obstructions there.

About the Author: Jim Locker is a technical guy who has done a lot of real estate investing and landlording. The experiences he writes about and advice he gives are either first hand, or in answer to specific questions posed by others. He is commonly known as jiml8 around the internet.