Lennox 80UHG3 - Combustion Air Blower doesn't spin

Timothya1

Hello All,

I am having some issues with my furnace (Lennox 80UHG3) and in desperate need of advice. My house was abnormally cold when I came home from work. After trying several times to "re-light" the furnace, I was unsuccessful. The furnace was working fine yesterday.

I noticed that the Combustion Air Blower (CAB) doesn't spin. When I turn the power on to the furnace it spin slowly for about 1 sec, and then stops. I can easily turn it manually with just one finger.

I removed the access panel to see the control board. The LEDs read as follows:
~LED 1: Slow Flash
~LED 2: On

The corresponding diagnostic code is:
~Primary and Secondary Limit Switch Open
~Combustion Air Blower Off. Indoor Blower On.

Any advise, suggestions, and/or opinions is greatly appreciated. If I haven't provided enough information, please ask any followup questions. Thanks!!

harleyrider

When was the last time that you inspected , and or changed your filter?

Timothya1

Harleyrider,

I inspected and changed the filter last night when I was trying to figure out what the problem was. The filter was black and clearly should have been changed months ago. I will definitely make sure to change it regularly moving forward.

yuri

with the tstat calling for heat that motor should get 120 volts. need to check that with a meter or call a Lennox pro.

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harleyrider

Tim the indoor blower is running because one /or more of your high limits are open ......from the dirty filter. Some times they reset on there own other times they need to be reset and or replaced.With those limits being open the furnace thinks its in a over heated state and is running the blower to cool itself off. The same applies to the combustion motor, it is NOT running because the furnace control thinks its in a over heated state, allowing the furnace to light would only worsen the condition.

Most likely you will need a service man out to get you back up and running.

Timothya1

Hello Harley,

After replacing the filter last night, I shut off the heater and thermostat. This morning I removed the control board (it has the LED's on it), and re-attached the same board. When I turned on the furnace and thermostat, the Combustion Air Blower stayed on and the burners heated up and heat was flowing throughout the house. About 1.5hrs later, I left for work and it was still functioning properly. I will check it when I get home this evening.

harleyrider

Sounds like the limits re-set them selfs.....Buy a lottery ticket

Timothya1

Harley,

Thanks for your help. I'm just curious...about how much would it have cost me to have the limits reset?

harleyrider

Don't know what they charge were you live for a service call, but I will say if I had come out it would be the trip charge of $109 and 1/2 hour labor@ $97.50 per hour. If the unit was dirty i would have suggested cleaning it for an additional $69. The key is that you would have a guarantee on the work, 30 days on labor and 1 year on any parts.

Timothya1

Oh ok, well it seems as if it's back to normal now. Hopefully, I'll be walking into a warm house this evening instead of a cold one. Thanks again. Take care.