Tip & How-To about Heating & Cooling

Gas furnace comes on goes out in 2 to 3 seconds.

This is a common problem with gas furnaces with ignters and flame rods. The flame rod is inserted into the burner and proves flame to ignition board. If this probe is dirty clean it with sand paper or steel wool. The probe is about 2.5 to 3 inches long with one wire attached. It may not look dirty but gets a clear coating on it from the flame and gas. One screw holds these in place and is very easy to get to and clean. Of course to reset furnace you must kill power to furnace.

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Why does it start, then shut down followed by 3 clicks?

  • Thermostat calls for heat
  • Venter motor starts
  • Air switch verifies vacuum
  • Igniter sparks, or glows - depending on furnace
  • Flame starts in burner
  • Flame rod senses flame
  • Burner continues to burn until thermostat stops calling for heat
By your description, I would polish your flame rod, it will be a metal rod that is insulated from the bracket that is screwed to the furnace case and it will have a single wire attached to flame rod,

Sep 29, 2015 | Intertherm 56000 Btu Gas Furnace

1 Answer

coleman dgaa furnace lights then goes out

If your talking about taking out the flame proving rod and cleaning it with sand paper or abrasive cloth and that didnt work, you may have a bad flame proving rod and it needs replaced. If the flame sensor is good, it could be the board not keeping the call to the gas valve, the gas valve not keeping the call, or your thermostat not keeping the call. Hope this helps narrow it down.

Dec 07, 2013 | Coleman Heating & Cooling

1 Answer

goodman furnace gmh95090cxac wont stay lit keeps clicking will lite then clicks back off what would be the problem

Hello, if the burners light but do not stay on for more than 10 seconds, I would clean the flame sensor. The flame sensor is a metal rod that is on the opposite side of the Igniter, sometimes it gets coated by oxidation and does not sense the burner flame and shuts the Furnace down. To clean to kill power to tje furnace, remove flame sensor and clean with a steel wool, then reinstall and start Furnce back up. If this does not work then most likely the Igniter is too weak to ignite the gas and will have ro be replaced.

Oct 29, 2012 | Heating & Cooling

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