Tip & How-To about Heating & Cooling

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.

Posted by on

Heating & Cooling Logo

Related Topics:

Related Questions:

1 Answer

Installed June 12, 2012 a new Ducane Bottle Gas Furnace. My furnace will run a normal cycle of around 10 to 15 minutes. Then 3 min later it will start again and run for 3 to4 minutes and shut down or


1 do you have a program or mercury buld mercury bulb.is usally a adjustable heat anticipator which a digital is fixed I recommend a digital t stat but also be advised that mercury bulb tstat are really phased out you could also have a issue with your main limit inbetween the heat exchanger wheather it is a cam stat or a normally closed limit but being a new furnace its more likely to be a n/closed limit will open if there is to much heat in supply box above the evap coil.you would need to take your delta temp reading within manufacture specs..or call aca or your local hvac company 770 932 8990 ask for mr.blaine to schedule your appointment today or are office staff thanx.

Jan 24, 2013 | Ducane 30400042 (LP)

1 Answer

On occasion, my furnace will not kick on at


If your Rheem furnace is less than 10 years old, it may store an error code to help you figure out if it is the furnace or the thermostat. Look at the circuit board for a blinking light. If you have to remove the panel that opens up the door safety switch, it will erase the code. Look for a small viewing port. Next time the furnace fails, prior to doing all the things you did last time, look thru the viewing port to count the number of blinks. Once you get the number, open the cabinet and on the wiring diagram glued to the back of one of the panels'\; there will also be an error code chart. It may give you a starting point where to look. If you have no error code, chances are that your thermostat is freaking out or has a bad connection. Hope this helps.

Dec 28, 2009 | Honeywell CT3200 5-2 Day Electronic...

1 Answer

mobile home furnace with central air unit water coming out of fur


You had the condensate from the furnace come loose look for a pvc pipe coming off the furnace it drains the high efficiency heater. I would really check out your hot water heater too.

Nov 25, 2008 | Heating & Cooling

Not finding what you are looking for?

635 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Heating & Cooling Experts

paulcarew

Level 3 Expert

2458 Answers

Dan Webster
Dan Webster

Level 3 Expert

8220 Answers

Donni Steen

Level 3 Expert

659 Answers

Are you a Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Loading...