The short answer
When the air is not getting where it should, the cause is usually the duct work, sometimes a zone panel, and rarely the unit itself. Damage and disconnects in the duct, closed dampers and a return that is too small are the common ones.
What you can check yourself
- Open the vents in rooms that are not used.
- Check that furniture is not covering a return.
- Check the filter size and condition.
- Note which rooms and which time of day: an upstairs room that is hot every afternoon points at the duct.
What gets checked first
- Duct work damage and disconnects
- Zone system and dampers
- Return air and the filter size
Repair or replace?
Duct work. Sometimes a zone panel. Rarely the unit.
When to call now
No emergency, but do not replace the unit before the duct has been looked at.
Ductwork and air quality: how we help