How To Solve Your Furnace Problems

"Not so simple" furnace problems. 

Problem: Your furnace seems to work until it tries to light, no such luck. When a furnace has a bad ignitor what they see most of the time is the following sequence of operation:
1. Thermostat calls for heat.
2.  Draft inducer motor starts.
3. Pressure switch senses the negative pressure produced by the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound.
5. The ignitor did not glow, the flame sensor does not sense the flame, so after 8 to 10 seconds the hissing sound stops with no ignition of gas.
6. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again.
7. Then the sequence starts all over again with no ignition of the gas.

Solution: You probably need a new ignitor.

Less likely causes:
1. You could have a furnace control board problem.
2. A limit switch is bad.
3. Rollout switch problem.

If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you most likely need a new flame sensor. If your furnace problem is in the "not so simple" description, they recommend that you give them a call so they can come out and fix it safely and make sure it's done right.