Where is flame sensor on heil furnace located

Check the condensate drain .

Check flames sensor is clean . check air filter is clean . check pilot is clean and strong .

heil furnace startup shutdown - YouTube

Furnace Not Starting - Clean the Flame Sensor - YouTube

That is hard to answer but I would say that for a furnace of that size you are probably looking at somewhere around 16x20x1. On older heil furnaces they often had the filter mounted inside the blower compartment so if the case you can just remove the cover and measure it. If not it should be located on the return air duct close to the furnace. Hope this helps you some. Thank you.

Go to Heil furnace \ there is a flame rod that sick into flame on burner. Clean with sand paper or steel wool. And retry furnace. Rus

Your flame sensor is contaminanted. Clean it with steel wool and party on!.
Watch this movie:
FLAME SENSOR TROUBLES


If you need further help, reach me via phone at https://www.6ya.com/expert/dan_73bbd84fe1d95b61

You need to remove the flame sensor on the far left hand of the burner. In has a single wire going to it in between the jets. I believe it is a white wire. A 1/4" screw holds it in place. It has a white ceramic base with a stainless steel looking probe that protrudes into the flame of the burners. Pull the wire off of it, then remove the flame sensor from the burner assembly.. Use steel wool to clean the metal probe until shiny. Re-install and enjoy your heat.

recommend getting a carbon monoxide indictor or having some one test it. with it being over 15 yrs old if checks good replace ignitor assy should fix it ok

Sound like a thermocouple, or flame sensor.
If it has flame sensor make sure you check micro amps to verify operation, because it might be the board that controls the sensor.