Why is the heater not warm when the truck's water temperature is normal?

[Polly]

Truck's water temperature is normal but heater not warm reasons are as follows: Dirty air conditioning filter: A clogged air conditioning filter will significantly reduce the airflow, thereby affecting the heating performance of the heater. Damaged water pump impeller: A damaged or slipping water pump impeller results in insufficient flow through the heater core, preventing heat from rising. Air pockets in the engine cooling system can cause poor circulation, leading to high water temperature and ineffective heating. Clogged heater core: The vehicle's heater works by using a blower to push heat from the heater core into the cabin. If the heater core is clogged, the heat cannot be dissipated properly, resulting in inadequate heating.