My Trane furnace which is 2 years old just started blinkind 4 times meaning open limit device. I replaced filter but still keeps flashing.

Is there any way to reset the fault??

How do I test the limit switch, I 've taken the switch out and blow into it and it seems to open and close like it's suppose to??

Any suggestions will be appreciated. Thanks:confused::confused:

What you are blowing into is not a limit switch but a vac/pressure switch safety device. Look on the wiring diagram on the inside of the blower door of your furnace. Try to follow the diagram to the real limit switch. When you find it see if there is a small reset button in the center of the switch. If so reset it. Naturally do this with the power turned off.

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Originally Posted by hvac1000

What you are blowing into is not a limit switch but a vac/pressure switch safety device. Look on the wiring diagram on the inside of the blower door of your furnace. Try to follow the diagram to the real limit switch. When you find it see if there is a small reset button in the center of the switch. If so reset it. Naturally do this with the power turned off.

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Thnaks found switch. I removed it and tapped it against the floor . I reinstalled it and furnace I now OK. I will buy a replacement switch just to be safe.Thanks

Glad you got it going