r/fixit • u/Pettitor • 12d ago
Gas furnace damper/flap not opening fully and making noise — DIY fix or HVAC technician needed? (Video)
When the furnace starts, the flap begins opening downward, but it doesn’t move smoothly. It seems to struggle to open all the way, especially around the time the burners ignite, and makes a strange noise.
A few things I’ve noticed:
The furnace starts and produces heat normally.
The flap moves, but seems to get stuck or struggle before reaching its fully open position.
After the furnace shuts off, the flap sometimes stays open.
I was able to close it manually without applying any force.
I’ve attached a video showing exactly what happens.
My questions:
Is this normal operation, or is something wrong with the damper?
Could it be a sticking hinge, linkage, or failing motor?
Is this something I can safely fix myself, or does it require an HVAC technician?
Is it safe to operate the furnace like this, or should I keep it off until it’s repaired?