Heater slow to blow warm air

2006 Corolla S - 134K miles

My daughter's Corolla only blows warm air through the vents when it's been running about 30 minutes. I checked the coolant, which was a bit low. I remedied this, but no improvement with the warm air. It's not throwing any codes.

What steps would you take to diagnose and determine the problem? Thanks in advance!
I should clarify that air blows fine into car. And that the engine temperature indicated on the dashboard is also normal. It's just that the air is only warm after the ~30 minute period.


New Member
Check the filter first to make sure is clean, then i would check the flap that regulates the temperature, make sure knob that regulates to hot and cold, the flap inside the ac opens and closes to select between cold and hot if isnt going all the way to hot then you will get warm heat