Well it depends on what type of furnace you have so cant really help you on this one know it's cold on your home xD lol sorry :/
It tells the furnace that it lit... Hence the name Flame Sensor.
If the furnace is direct ignition, The HSI or spark ignites the flame. A flame sensor passes current through the flame, if current is present the main.
Is there a flame in the furnace. Precisely where is this air coming from and how strong is it?
its hot!
The main circuit board in your furnace sends a small ac signal to the flame rod so now you have an ac potential from the body of the furnace to the flame rod, When the flame comes on between the body of the furnace and the rod it rectifies the ac in to dc, The flame actually acts like a diode. When this dc voltage is sensed by the control board it knows there is a flame present and thus keeps the gas valve on. Hope this helps
An oil fired furnace works by using oil and a flame. The oil is sent through a tube to the burner area of the furnace and when the oil is ignited with a lighter, the flame can be adjusted according to how much heat is necessary.
check your flame sensor
The gas furnace pilot (flame is lit all the time) is sometimes referred to as a pilot light, but no matter what you call it, its purpose is to serve as a small ignition flame for the gas burner. And when this little flame fails to operate properly or go out, it's one of the most common reasons a gas furnace will fail to operate.
flame sensor
Twist the collar.
warning: flame roll out can cause serious injury 1) turn service switch off at the furnace 2) adjust thermostat so set point is 5-6 degrees above room temp, set t-stat for heat, and set fan to auto 3) remove ignition compartment door of the furnace as opposed to the door enclosing the indoor blower motor 4) turn the furnace service switch back on 5) do not look directly at the combustion burners as flame will shoot out of the burner compartment 6) observe the ignition finally proper ignition is confined to the area intended for combustion, with a blue flame. a roll out will cause the flame to ignite beyond the burners and may even blow beyond the blower compartment. further, a roll out can persist beyond the initial ignition sequence.
It is Raceway Adiabatic Flame Temperature present in the front of tuyears.