Hi

I have a natural gas Trane XV90 furnace approximately 5 years old (I think, it was already installed when I purchased the house last year). I have a separate AC unit outside (approx 9yrs old) - no problems with the AC. My thermostat is a "peak saver" by Honeywell, programmable.

I have read NorthernHeat's troubleshooting tips, and following his described sequence of operation everything is OK up to the point that the HSI lights the main burners. At this point the burners stay lit for about 5-10 seconds, the fan starts and then the burners shut off. The fan continues to run. About a minute later the HSI once again lights the burners and then they go out again. And so on.

The temperature in my house has stayed at 18C while the thermostat is set to 21C, with the furnace running like this all night.

Thanks in advance for any help that can be directed my way. I`m located in Ontario, Canada and it is already feeling like winter up here!

I turned off main disconnect and gas and left system off for about 30 minutes while I started a fire in my fireplace to warm up lol. I checked connections for and position of flame sensor. I closed up the furnace and turned on gas and power. After about a minute it started up and is working OK now. I'm not really sure what I did to make it work. Is it possible that the flame sensor is faulty? Any info would be greatly appreciated as once the snow flies I really don't want a repeat of this problem.

Clean flame sensor or test like a professional would do.