Hi, new to the forums - and only came here because I am unable to afford a full-on repair or new furnace. I'm not mechanically inclined but can learn when I have to.

My Sears/Kenmore Counterflow Wall Furnace which is way more than 10 yrs old - is gas heat with an electonic ignitor.

The thermostat on the wall clicks and tells the furnace to open the gas valve. The gas valve opens and intermittantly it will ignite the gas. Within seconds of lift-off, there is a loud banging/clicking noise that repeats for about 10-15 seconds and then the gas valve shuts off the gas.

The electronic ignitor is a Honeywell 5825d, I only know this because that is what it says on the face of the little black box thingy (yes, thingy!) that ignites the gas. I have cleaned all the contacts/sensors and vaccuumed out the inside of the unit to ensure that no dust is interfering in the ignition process. All the wiring is connected, not loose. The durn thing fires up only sometimes. Right now, it's completely off.

I have restarted it repeatedly over the past week, both with the directions inside the unit about lighting the pilot light. (It's electronic, so lighting it manually is not an option. I do know this much, being a girl who can read directions and occasionally follow them as the manufacturer intended) I've managed to get it to light only about 10% of the time that I restart it. I've turned off the thermostat, shut off the pilot light switch, waited more than five minutes - sometimes more than an hour - to turn it all back on and try to fire it up. Again, sometimes it does, mostly it just doesn't. I've moved the temperature on the thermostat, I've even adjusted the thermostat differential thingy. Again, the thermostat fires and clicks and tells the unit to open the gas valve. It can't be the thermostat.

I think it's the Honeywell electronic ignition and sensor that doesn't work properly and the sensor is telling the gas valve to shut off. I have researched online and the part is clearly obsolete.

Is there a way to get a replacement part for the Honeywell 5825d?

If not, is there an optional part from another manufacturer that works universally that I can buy and have installed?

Am I possibly wrong on what the issue is?

Any thoughts on what it could be if I am?

Do not use the words "user error" or "thingy" in your response, please. Be nice. Thank you.

you would have been my hero 3 weeks ago when it was 20 degrees out and i had no heat. because i do know for a fact now, that that would have worked and saved me the cost of a new heater. also, i ended up finding the replacement part for the honeywell black box thingy that is obsolete - after the issue is resolved, of course, and a new heater was purchased. maybe everyone's delayed response to my issue will help someone else in the future though who doesn't have the means to buy a new one.

an hvac guy from the neighborhood explained all this to me after the fact and showed me how to take the flame sensor out and clean it so that it "shines like a quarter".

as a non-mechanical person, i'm kind of proud of myself - even if it was an inconvenient lesson to learn, being without heat and all - but i learned how to find replacement parts for obsolete components and also what the different components inside my stupid heater and what their function is.

i just pray to god that i never have to know this stuff in the future. thanks for the suggestion though. i do know that's all it would have taken because the heater we removed works now, after doing just exactly what you suggested. thank you for the response.