Furnace intermittently stops working
 

Just wondering if there's any HVAC folks in here that can help me with my issue with my furnace.

It's a gas furnace (in the basement inside of an enclosed area in one of the bedrooms) that intermittently won't "ignite" (please forgive my non technical terms) :)

Basically what happens (and it's usually happening overnight) is that the electronic igniter (the element that glows and ignites the gas) won't turn on for some odd reason. The fan is running and it's cold enough for the heat to be going but because the igniter doesn't turn on, the gas doesn't turn on and therefore there's no heat.

What we do every time (and this fixes it for a few months) is basically take the access panel off the furnace (so we can see the igniter) and press the switch that is usually depressed when the panel is in place. Every single time we do that, the element will light up and gas will flow and all is good again. I put the cover back on and we're in business again and all is good again for another month or so.

I'm baffled as to what the reason for this is. It doesn't seem like there's any specific component failing because it all works if I push the switch by hand. I had a theory that perhaps it was oxygen starved and couldn't get a flame going, but then does an electronic igniter need oxygen to turn on in the first place?

Any suggestions on what the problem could be?

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Mine does this too. There is a heat sensor probe at the pilot light which I thought was the problem but after replacing the probe, the pilot light still goes out about twice a year. You can try replacing that. It's only about 10 bucks.

I'm theorizing that a big gust of wind might be coming down my air vent and blowing out the pilot light???? Maybe I have a wrong type of capping for the air vent??

The thing is that it's not a pilot light. From what I know, a pilot light is just a flame that's constantly on and lights the gas when it's turned on. My furnace has an electronic igniter which is basically an element (much like a stovetop) that heats up and glows and ignites the gas when the thermostat turns on the flow of gas.

Thing is that when we have this problem, the igniter doesn't turn on. (I can see through the vents that it's not lit) but manually hitting the panel closed switch will turn it on every single time.

Whoops sorry bro, I scanned your post too fast and never seen a setup like yours yet. I'm living with old tech.

I'm still interested in seeing the responses for answers...

Could be a number of issues. The ignitor itself is known as a hot surface ignitor. It's controlled directly by the control board. But depending on your furnace model, there may be some conditions that need to happen before it will ignite. I don't think it's the ignitor itself, but possible the board or another sensor, or a blockage somewhere.

If you have a newer furnace (like 90%+), by opening the side panel, the power to the system will usually cut off, and by pressing the button to start the furnace, you essentially "rebooted" your furnace controller, hence why it may start everytime you open it up. These furnaces also usually have other sensors for pressure on the gas line, on the aux blower for combustion, etc. The controller board on these somtimes have some LEDs that will flash a certain sequence indicating the problem (like PC beep codes if you need an analogy), sometimes viewable from the outside of the furnace without taking off the cover (and removing the cover may clear the codes).

The newer furnaces also have dedicated plastic intake and exhause ususally on the side of the house, and at this time of year, things may "live" inside them like birds, and cause improper flow and sensed by the furnace.

Thanks for the info! I'll see if I can find the LED boards. I'll also see if I can check the vents.

What's the brand on your furnace?
I had the same problem, there's a heat sensor that is in the path of where the flames come out. It's l-shaped and about the size of a paper clip. Take that sensor out, clean it with steel wool.

Take a look at your thermostat. It should be upstairs in your main living area somewhere. Check to see if it is working properly. What have you set the temperature to? Some of the digital ones will have a little picture of a flame to indicate the heater is on. Bump up the set temperature (higher than the actual room temperature) to see if it is responsive. The thermostat should be sending a signal down to the furnace telling it to turn on.

Assuming the thermostat is okay, move on.

What the likely problem is the THERMAL COUPLE.

Basically how your furnace works is the following:
-House is cold, thermostat detects it's cold
-Thermostat sends signal to the furnace to heat up
-Funance lights up and heats up the box that holds air
-Thermal couple is a little thermometer that ensures the pilot light is on. It looks like a piece of metal that sticks into the flame. If there is no flame, the Thermal couple will shut off the gas. If the Thermal couple is old and eventually gets charred up, it wont sense anything and always think there is no pilot.
-The thermostat is there so you can adjust the range of the air you want blowing out.
-When that box/air gets hot enough it sends a signal to tell the fan to turn on.
-Then the fan blows hot air through out the house.

It's a cheap part to buy and easy to replace, just plug and play. Just take the old one out and bring it into any old school appliance store and they should have them in stock.


Edit:

oh shit, i see you don't have a pilot light... well i'm sure there's something similar for the newer style furnaces in terms of a safety device to shut off the gas. I googled my furnace problem (by no means a pro so take my advice as you will) and thats how I came about to fix it myself. It costed about $20 and no labour so couldn't really go wrong...so long as you remember to turn off the gas first.