My furnace is 5 years. Every time it calls for heat it fires up just fine but then after 3 sec. the gas turns off, it repeats this cycle until it locks out the system. I have reset the system, checked all the wiring for loose connections but cannot get it to run. Please help me.

Not real familiar with trane units, but I'm betting there is a flame senser. Locate the flame senser, clean it and see if your worries go away.


Little more info... The flame senser will be located directly in front of the burner, on one side or the other. Remove, clean with sandcloth, steelwool, sandpaper, or any abrassive cloth. Reinstall. And let me know if it works. Like I said, I'm not familiar with train, but you are looking for a single probe

I greatly appreciate the help. Thank you.

Perfect answer. Pulled out the sensor and though it did not look that bad, the resistance across was pretty high. Cleaned as you suggested and system fired up with no problems. Thank you!

Glad it worked for you too.