Any heating and cooling Guys out there? I have a question

Some of the older dryers had a lashup with a temp sensor. I have not kept up on dryers. If it fires for fifteen seconds and dies, it's much more likely to be a plugged vent problem, line plugging something like the blower wheel, or a blower wheel loose on the shaft

In the late eighties I maintained laundry gear for several local laundries owned by a family. I LOVED the Maytag stuff. Took me all of about 1 minute to pull the front cover and remove the drum. You could clean those out in nothin flat. I've seen all kinds of stuff in the blowers and ductwork, including several calibre of live ammo

There are several ways, typically, that flame rectification is set up

Some is right off the main burner, that is, there is no pilot

Some light a pilot first, "prove" the pilot then allow the main to fire

Some are spark, some are "hot surface," or a glow device

And, some have the spark or hot surface device combined into the sensor. This involves a tricky internal circuit. BE CAREFUL with hot surface as these have line voltage (120VAC) on them. Keep your fingers and tools away from them.

Flame rectification is pretty much the "de facto" method. It is pretty reliable and really safe. Pretty much "fail" in safe. Years ago, they tried photocell, which does not work well with gas or LP and Carrier used to have a crappy thermostatic pilot sensor deal that was a REAL PITA Thermocouples were "OK" but Honeywell made a BUNCH of gas valves "back when" that could fail even though the pilot safety was "dropped out."

Once in awhile, tho, you will find a gas valve STUCK OPEN. Last one I came across was on a gun burner conversion in an old old convection furnace, converted from oil or coal. It was a cold day, and had got up to the middle 80's in the office. "The girls" could not get the thermostat to kill the heat. I went downstairs and the burner was wide open. Killed the main power and it was.........WIDE OPEN.

If this had been a weekend and left on, we'd 'a had a fire.