i have a 99 accord 5 speed and i just replaced the thermostat( old one was stuck open) and gave is a coolant flush. the heat wasn't to good when i bought the car a month ago and it still isn't good after the maintenance i just did on it.
any thoughts of what could be causing this?
thank you

 

How clean was it inside the thermostat housing? Maybe the heater core is part obstructed? Did you flush it with some cleaner or rinse it with water?

Did you bleed air out of the system? Was the heat turned way up when you did that?

In the engine compartment, find the valve on the heater hose. With the key on, turn the temperature dial & verify that the cable moves and it's connected to the valve.