Troubleshooting Carrier Furnace on Startup

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jeffc
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Troubleshooting Carrier Furnace on Startup

Post by jeffc » Thu Dec 15, 2011 3:07 pm

My Carrier furnace starts up normally (thermostat working, blower on, ignitor glows, flame comes on), but shuts down after about five seconds. Replaced flame sensor with no effect. What other safety mechanism could be causing the gas to shut off after only a few seconds?

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juster
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- Troubleshooting Carrier Furnace on Startup

Post by juster » Thu Dec 15, 2011 4:35 pm

lack of proper air flow, did you check your air filter?

heatseeker
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- Troubleshooting Carrier Furnace on Startup

Post by heatseeker » Fri Dec 16, 2011 9:17 am

is there a good flame at the sensor?

Freon
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- Troubleshooting Carrier Furnace on Startup

Post by Freon » Sat Dec 17, 2011 11:08 am

Shutting down so quickly could indicate either a flame sensing issue or a draft inducer pressure issue. If you can follow theduke03's recommendations you may have less testing to do. But since you replaced the flame sensor you could try TEMPORARILY jumping the pressure switch on the inducer blower. If that stops the problem, then check the flue for any type of blockage.

Lastly, if the inducer and flame sensor are good (new), then I would suspect the control board, especially if it's positioned close to the firebox (excessive heat kills electronics).

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