Furnace seems to run fine, then shuts off.

[presslandw]

I am trying to assist my parents with their furnace which seems to be having issues staying lit after not being used over the summer. I was able to light the pilot easily and the furnace fires up immediately. After about 10 minutes, the pilot light is extinguished. It seemed to function fine otherwise. Is there a likely culprit in this situation?

Photos here:
https://imgur.com/a/lDo71y4

Any advice is appreciated!

 

[Dana]

When thermocouple flame sensors are nearing end-of-life they begin to exhibit flaky behavior, occasionally causing the pilot to turn off.

Is the tip of the thermocouple sensor sufficiently close to the tip or at least the blue part of the flame? If not, see if adjusting it for a bit more flame contact between the tip of the thermocouple and pilot rectifies the problem.

Is the thermocouple clean, or is there a soot or flame-seared varnish on it? If it's suspiciously dirty, cleaning it up with a plastic scouring pad (not steel wool, not sandpaper, which may shorten it's service life) may do the trick.

Is the pilot flame mostly blue? If it mostly yellow, the tip of the orifice where the gas exits may need a bit of cleaning (with your sister's tooth brush, no toothpaste. )

If it continues to misbehave, replace the thermocouple. Most are good for 15-20 years, but failure at 10 years isn't rare. As repair parts go they're pretty cheap.