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My Lennox C33-60D-2F furnace isn’t heating. The indicator…

Customer Question
My Lennox C33-60D-2F furnace...

My Lennox C33-60D-2F furnace isn’t heating. The indicator LEDs are slow alternate flashing yellow.

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

Filters were just changed, and the thermostat settings haven’t changed. We keep it set for 68. The furnace was running fine earlier, but when I noticed it getting cold in the house (64) I turned the thermostat to 70. When the heat and fan didn’t turn on, I came down and checked the LED lights.

Contractor's Assistant: Do you plan on doing the work yourself?

If I can, I would like to. I don’t have much money for repairs, but it’s only 20 degrees

Contractor's Assistant: Anything else we should know to help you best?

What should I be looking for to see if I can fix this myself?

Submitted: 8 months ago.Category: HVAC
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Answered in 2 minutes by:
12/29/2017
HVAC Technician: airheatman, HVAC Technician replied 8 months ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,545
Experience: Furnace, A/C and heat pump specialist.
Verified

Can you look inside the burner compartment on label on side panel and get me the model on your furnace? The model you listed is the ac coil

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Customer reply replied 8 months ago
While I was waiting, the furnace kicked on. The lights are now flashing simultaneously fast to indicate normal operation. And the heat is working. Should I still pull off the panel to give you the number? This could be the defining of a problem, and I’d like to find out, but I’m not sure if I should take off the cover while the burners are going.
Customer reply replied 8 months ago
Beginning * of a problem (damn auto correct)
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

If it is working it will be hard to troubleshoot.

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Customer reply replied 8 months ago
Ok. Then I guess there’s nothing I can do. Thank you very much, and I pray this keeps working. It’s only in the 20’s at night.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

If you want to remove panel in front of burners and get me model I will tell you what the error code indicates so you might have an idea of what was happening

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Customer reply replied 8 months ago
Can I do that while it’s running?
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Absolutely.Just top panel in front of burners

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Customer reply replied 8 months ago
G40uh-60d-135-04
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Thanks. Would you say the alternating was a slow flash or fast flash?

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Customer reply replied 8 months ago
Slow
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Alternating slow flash indicates an issue with a loose wire to gas valve,board failing to tell gas valve to open or gas pressure in or out of valve.

Each would require different troubleshooting steps.

1.Simple enough to just make sure all wires are secure and connections are clean

2. Would require testing to see if board is sending 24v to valve

and 3 would require a manometer to test the gas pressure in and out of valve.

If it is 20 degree, it could possibly be gas pressure.I have see gas lines from the gas company actually have enough moisture in lines under ground to freeze and prevent enough gas supply pressure.

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HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Here is the diagnostic chart.If you have further questions, please let me know.
Thanks for letting me work with you.If my answer has been polite, professional,and thorough, please click one of the ratings before you go. If you still need help let me know!.Expert is not paid for assisting you until you rate answer.Feel free to follow up for 30 days at no additional cost. Bonus always appreciated if you feel justified.
To rate answer, please select one of the stars on the page.

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Customer reply replied 8 months ago
As I’m sitting here, the fan is running, but there are no flames. It has tried to turn on 3 times so far. The area on the right turns bright orange, there’s a click, and then the flames burst for less than a second. Now it has turned off, and the LEDs are back to alternate slow flashing.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

OK if you hear the click that pretty much means board is probably signaling valve to open and solenoid is clicking but gas not coming from valve.

Most likely a gas supply pressure issue or failing valve.

Do you have other gas appliances and do they work properly? If you have a gas stove look and see if flame is as high as normal

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Customer reply replied 8 months ago
flame on gas stove is normal.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

If flame looks decent when it does light, lets locate and clean the flame sensor. See video below

https://www.youtube.com/watch?v=tYwR9qL4lnk

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Customer reply replied 8 months ago
Ok. I did what the video said. And the sensor didn’t look to dirty.
Customer reply replied 8 months ago
The lights are still alternating slow yellow, and the heat hasn’t kicked back on even though the temp has dropped below the thermostat being set at 70. Thermostat currently reads 66 degrees.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Next step will be to get a manometer or have a tech come in and check gas pressure in and out of valve.

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Customer reply replied 8 months ago
Ok. Thanks. I’ll have to see if I can find a technician then.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Wish we could have solved but if flame sensor is clean and connections are good, the manual popints towards an issue with valve or gas supply.If you have further questions, please let me know.
Thanks for letting me work with you.If my answer has been polite, professional,and thorough, please click one of the ratings before you go. If you still need help let me know!.Expert is not paid for assisting you until you rate answer.Feel free to follow up for 30 days at no additional cost. Bonus always appreciated if you feel justified.
To rate answer, please select one of the stars on the page.

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