Hello,

I have a York Furnace Model FG8B07512MU11A and it recently noticed that the furnace shuts off early, even though the thermostat is still set to higher. I can turn the thermostat off and then back on and the heat will start right up, but it will always stop 5-10 minutes later. It'll still turn on throughout the day on its own, but will never run longer than those 5-10 minutes.

I opened up the furnace and saw that the LED is blinking red 7 times which is for "Ignition Lockout Due To Retries." After some research online, I read that this could be due to buildup on the flame sensor, so I pulled it out and cleaned it with steel wool. It wasn't too dirty to begin with though. That didn't seem to help. I did notice that the sensor was a little off center from the flame, so I adjusted it to be center, but it didn't help. I also read that it could be an airflow issue with the filters, so I swapped those out and even tried running the system without the filters, but that didn't seem to change anything either.

I made a video of the furnace starting up and eventually running into the issue: https://www.youtube.com/watch?v=5_6XPlIMx5g

Important Timestamps:

1. 0:15 - Ignitor Starts
2. 0:26 - Gas and Flames Start
3. 0:30 - I show that the flame sensor is directly in the flame
4. 0:45 - I show the LED is slow blinking amber color, which is for running normal with gas.
5. 1:00 - Fan Starts for inside heat
6. 4:40 - Flame Stops (Maybe gas cuts off? I'm not sure)
7. 4:45 - Ignitor tries to start flame again
8. 7:00 - System gives up and returns error code of 7 red blinking lights

Unfortunately, I don't have a ton of experience with furnaces, so if anyone has any ideas, I'd really appreciate it! Thank you!!

 

It's hard to tell from the video but is the blower running?

 

Yes. Both the blower and the fan for inside (not sure the name, but it pushes the air through the heat vents inside) both seem to be working as they should.

 

I don't think you have an air flow issue. I noticed you are getting flash code 1 when it is running. Could be a weak flame signal.

Flame sensors rarely go bad but it does happen. I would replace it.

 

To me that flash code looks like the "Slow Amber" that's listed on my fault codes list and that stands for "Normal operation with call for heat." There is a "Rapid Amber" that stands for "Low flame sense current," but that flash didn't look that rapid to me.

I was wondering about just replacing the flame sensor, but didn't know if it could be something else. They're cheap enough, so I'll try that out and report back how it works. Thank you for your assistance!

 

OK the manual I am looking at shows normal operation the led will be off.

 

The fault codes are in red. Are you getting any red flashing lights ?

If no red LED I'm considering a problem in the gas valve, valve wiring or the board itself.

Check for a red LED after the flame fails the first time. Use the sight glass.... don't open the door.

 

Okay, I just tried it again with the door closed, but still kept an eye on the light. It stayed the slow blinking amber color until the flames went out, then it turned to the green slow blinking light while it tried to relight a few times. The light never turned red until the end, when it gave up and then started that same 7 blink error code as before.

This time around, after the error code, I tried turning off the furnace and back on to see what it'd do. It started just like in my video, except there wasn't any ignition. I could see the igniter glowing again, but it was like the gas wasn't coming out. The light stayed the slow blinking green while it tried to ignite a few times, but then ended with the same 7 red blinking error code. I tried turning it off and on again after that just to make sure that's how it'd still act and it did, so it seems to be something that lingers for a bit. Now that I'm thinking about it, any time I've tried restarting before there was probably at least 10-15 minutes since it shut off on its own. This was the first time I tried immediately after it shut off.

Edit: So I decided to try to restart it again after writing this message and this time it started up and the flame started as well. So it seems like it needs at least 5 minutes or so before it can get started up again.