[Oomfh]

Installed new thermostat, flushed heater core backwards, ran coolant system acid flush for several days. Discovered heater core is hot - but little to no heat is coming into interior.

 

[ilikeike]

Is the fan blowing air into the interior ?
Are the cables from the control panel working the doors in the heater box ?

 

[Everett#2390]

Welcome, Steve,
Since 4th Gen, I would say the temp door actuator is broken.