Why is my furnace blowing cold air with a red blinking light?
A furnace blowing cold air and flashing a red error code often indicates a tripped pressure switch or an issue with the inducer motor preventing ignition. This stops the unit from heating your home, leaving you with unheated air running continuously. Fortunately, some underlying causes like blocked tubing can be checked and fixed at home.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Checking control board voltage with a multimeter
- 2Manually blowing into the pressure switch hose to test the switch
- 3Inspecting intake and exhaust vents for blockages
- 4looking up the error code on the back panel or diagnosis chart
- 5having a reputable company do a safety check and maintenance
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Hi! Ive got a Concord 90 plus high efficiency furnace from 2009 that's dx light blinks red 3 times. Is this something simple that could be fixed?”source ↗
“This morning my wife tried turning on the furnace and it was “only blowing cold air”.”source ↗
Where this came up
People with this problem also raised
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- 2Furnace won't turn on after new AC installation
- 2How to check if a vibrating radiator is caused by a bad fan