This furnace troubleshooting guide will cover furnaces that burn natural gas or propane. You can use our electric furnace troubleshooting guide for a forced If the burners come on but do not stay on for more than about 3 seconds, the flame sensor could be dirty or the furnace control board could be bad.Disconnecting is quite easy on newer model furnace blower motors as each wire uses a spade connector that connects it to the furnace power control board. On older model furnaces, you may find that the wiring is connected to a relay and control box using the wires directly and fastened with screw joins. Jan 16, 2018 · That's the click. That relay supplies 12V DC to the furnace control board to start the blower. Then after the blower gets up to speed, the sail switch closes and the board opens the gas valve and fires the igniter. If the blower doesn't start, you might have a blown fuse in the fuse box, or a loose wire at the furnace, or a failed furnace board. With over 50 years of experience in the business of helping Canadians make their homes comfortable all year round, Reliance Home Comfort™ is your premier source for furnaces, air conditioners, water heaters, furnace repairs and service, plumbing services, water treatment, smart home systems and more.