DIY Home Improvement Forum banner
1 - 3 of 3 Posts

· Registered
1 Posts
Discussion Starter · #1 ·

I've got a Bryant 373lav furnace that is giving me error code 31. When it runs, it blows air but does not produce heat.

If I reset the limit switches it will produce heat and function normally for about 5 minutes before reverting back to code 31. I repeated this process while resetting one switch at a time, and found the culprit to be the Blocked Vent Safeguard Tube and Switch (Component #9 on page 3 in the manual).

Does anyone have a suggestion on next steps to further diagnose the problem? Could it be that the limit switch is bad, or is it more likely a legitimate vent blockage?


· Hvac Pro
25,116 Posts
Those switches never go bad.
Check your chimney for blockage.
Where the vent pipe attaches to the furnace remove it and look inside for dead birds. Yours is a reverse/counterflow I believe so that may be hard as it goes thru the furnace cabinet. Birds get gassed and fall in sometimes and I have had them go all the way down to the exhaust/ventor fan.

You may also have a cracked heat exchanger and need a experienced Bryant or Carrier ( same company ) Pro to check it. Could also be overfired.

If you have a negative air pressure in the house caused by a fireplace or running kitchen exhaust fans and a clothes dryer at the same time it can happen.
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.