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Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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Bryant furnace will not ignite. What could be wrong?

Resolved Question:

Bryant gas furnace (Model #  310AAV066110AAJA) will not light and heat. I smell no gas and there is no sound or sign of igniter activity as would normally happen when it sparks and lights gas. Fan can run if we set our thermostat to fan "ON" mode rather than "Auto." If I turn the thermostat "Off" and back on to heat it will start up for a moment but never produce heat and just stop. Restarting the unit over and over will not get it to light up and heat. We already had to replace the igniter with a new one two years ago, but it still looks fine. The furnace is a whopping 5 years old maybe.
In the lens inside the front cover the red LED/indicator blinks slowly a few times and stops, then stays on a while, and repeats the same.

Submitted: 7 years ago.
Category: HVAC
Expert:  Matthew replied 7 years ago.
Is the inducer draft motor running?
Customer: replied 7 years ago.

Not sure. I do hear a motor sound other than the main fan as the unit attempts to start up, but how do I check it? Can I do this with the main front cover off?

Expert:  Matthew replied 7 years ago.

The inducer motor is the small motor hooked to the vent pipe going out of the house. This is the very first thing that comes on during a heat call. This has to be running in order for the pressure switch to prove and allow the igniter to light.

Find the pressure switch; it will look like this.

There will be a rubber hose that attaches this pressure switch to the inducer draft motor housing. Take this rubber hose off and blow through both ends. Then take a paper clip and clean out the tiny port on the inducer housing where this hose slides on.

Put it all back together and try the furnace again. Let me know what happens.

Customer: replied 7 years ago.

Ok that device and hose was found, tube was fine and is clean inside. Air goes through OK. Furnace does buzz a while when on.

Expert:  Matthew replied 7 years ago.

This blink code you are seeing will give us an idea of what is failing. The code is a two digit number. The first digit is the number of short blinks. The second digit is the number of long blinks. Then it will repeat. So find out what this code is for me please.

Customer: replied 7 years ago.

I can, tried before but seems confusing.
On a side note: There was a bit of a hot smell. At least once I noticed that. In the world of electronics would tell me I need to find a bad electrical part.
Also on the top of the gas pipe I noticed some shredded material like a little bit of leftover wood carvings...odd. Did that come down from something above it in there? Outside of furnace covering is clean.

Ok I watched that LED several times through its cycle. I believe what I am seeing is one very short and two long. 1 Short, 2 long, and then it repeats.

Expert:  Matthew replied 7 years ago.

Not sure what the wood is. Maybe they drilled a hole in a board or something above the furnace and these shavings dropped down on it.

From you describing a burning type electric smell and the humming noise you referred to earlier I think your inducer motor may be bound up and not turning. This would cause the furnace to not ignite.

Let's do this.

Take the two wires coming off of the pressure switch you found earlier. I believe they are an orange and a yellow wire. Turn the power to the furnace off and unplug these two wires.

Now with the wires hanging, unhooked, turn the furnace on. Once power is restored to the furnace, connect these two wires together with a piece of metal of some sort. No worries, this is just the common side of a 24v circuit. It will do you no harm. At the very most it will give you a tickle if you happen to touch he actual metal on the plugs. It will feel like a 9v battery when you stick your tongue on the end, but just handle the plastic sheath on the wire only and you will be fine.

With these wires hooked together see if the igniter glows. Let me know.

That is code 12. Code 12 is displayed any time you cut power to the furnace off and back on. It will flash this for 90 seconds with the main blower running and then it will either go into ignition sequence or it will become a different blink code telling you what the actual fault was.

Customer: replied 7 years ago.

I think I agree that inducer motor is suspect as we have heard some odd noises from the furnace recently when it ran, was not main fan doing that.
OK I tried removing and shorting those two connectors together, no joy.
Does it take an HVAC person that can work with gas to replace that?

FYI - I have multimeters and am a long time pro at electronics so I am fine with testing things, low voltage especially.

Expert:  Matthew replied 7 years ago.


Bypassing the pressure switch like this should make the igniter come on. When you say you shorted the two connectors together you mean you connected the two loose wires correct?

This should make the igniter glow unless the igniter is bad. By connecting these wires together we have eliminated the venting system from the equation.

The only thing is that you must allow the furnace to send the signal to the inducer motor to start up before you can short out the two wires. So it is essential that you start the furnace up with the two wires unhooked then after about 10 secs once the furnace power is restored you hook them together or the bypassing will not work.

Ok lets test the igniter.

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Unplug the igniter at it's little white male female plug connector.

Hook the pressure switch back up the way it should be.

Now let the furnace start up and see if you are getting 120v to that plug going to the igniter. With one lead on each prong of the plug it should show 120v.

Take in mind it takes a good 90 seconds for this signal to be sent to the igniter once power is restored to the furnace and the inducer motor comes on.

Customer: replied 7 years ago.

I connected the two together as instructed after disconnecting. Maybe not a full 10 seconds. I can try again. Also do I have to shut the breaker off to the furnace or is the wall switch by the furnace that turns it off (or A/C) enough? At no time did that inducer spin. I did not notice a glow on igniter but can try again. There was no popping or sparking sound.
Were those codes of no help?

Expert:  Matthew replied 7 years ago.

The switch on the wall is fine.

I posted earlier about the codes. I will cut and paste what I said here again.

"That is code 12. Code 12 is displayed any time you cut power to the furnace off and back on. It will flash this for 90 seconds with the main blower running and then it will either go into ignition sequence or it will become a different blink code telling you what the actual fault was".

Now when you cut power off then back on you have to let the furnace go through this 90 second purge while it blinks this code 12. After this 90 seconds then you can go into bypassing the venting system like we talked about earlier.

Customer: replied 7 years ago.

OK, the LED goes solid on after the 90 seconds, so no error code then.
I saw the inducer motor outer spinner/fan gizmo try to move and I helped it a little. Sure enough it tries to turn more and more, but is making noise and cannot really spin up. At that moment though the signals / power was obviously there to make it run.

Expert:  Matthew replied 7 years ago.

If the motor is getting the 120v but doesn't spin then that has to be the problem. You should be able to jump the pressure switch out like I told you earlier once the inducer gets this voltage and it should light the igniter and start the furnace, but if you can visibly see the inducer trying to spin and not spin then that is your problem.

That is the replacement motor for your furnace. It is up to you if you want to try and do it yourself or if you want to get someone out there to do it. Just know that if you purchase parts on line and they are not installed by a licensed professional the manufacturer has the right to void the warranty on your furnace.

Matthew and other HVAC Specialists are ready to help you
Customer: replied 7 years ago.

Do we need the draft-inducer motor for the unit to run safely, so if we bypass to see if the furnace runs otherwise? I plan on getting the part asap if I cannot clean it up and make it work smoothly again.

Expert:  Matthew replied 7 years ago.

The bypassing of the inducer system is only for testing correct. You can not run the furnace without an exhaust system working properly. This would be very unsafe.

Customer: replied 7 years ago.

That is what I thought, thanks. Here is what we did though. Removed the part, dusted her off and shot lots of spray lube into the bearings only, cleaned up any excess lube and reinstalled. Furnace now working fine!

Expert:  Matthew replied 7 years ago.

Good deal. It could have just been catching on something causing it to stop and start. Hopefully you will get some life out of her, but this could not have been good on the internal windings so you may just want to look into seeing if you can get it swapped under warranty. A furnace this old should not have these types of issues.