Trouble shooting your gas Furnace

If you are having trouble with you gas furnace they are really not that complicated to figure out. Most of the newer gas furnaces within the last 10+ years have a flash code on the circuit board inside the furnace. The trouble codes are in flashes. For example: 1 flash means ignition problem, 2 flashes mean vent pressure switch, 3 flashes means control board problem and so on. The first thing to do would be to check for a sight glass or window in the blower door to see if there is a flash code. Then you can pull off the blower door to check to see what the code represents. The code chart is usually located on the inside of the blower door.
If there is no flash type board in the furnace it still pretty simple to trouble shoot. First thing is verify that you have power to your furnace. You can do this by checking voltage with a simple meter. Check for voltage at the door switch since this is usally where the power starts. If there is power there then check for voltage at the thermostate between the R terminal and C for common. If there is power there then you need to go back to the furnace and try to figure out where the power is stopping. With the power to the furnace off start to check the safety switches. With an ohm meter or a test light you can start checking for continuity across your safety switchs. Check the roll out switch that is located near the burners if thats okay, Check the high limit that is usually located up higher on the front of the furnace that has two wires going to it, if that is okay then check your pressure switches and these you will have to check with the inducer or vent motor running. Hope that this information is helpful and if you don't feel comfortable using an electrical tester be sure to call in a professional HVAC Tech. to look at it.