2003 Buick Century

Hi winstonscamp. If you have a temperature gauge on the dash, and it is also taking longer to reach a normal reading, suspect a thermostat that isn't closing completely when the engine cools down. If the engine is reaching normal temperature as fast as normal, and just the heater is slow to produce warm air, I would suspect a partially plugged heater core, but based on your comment about it working fine, I'd look at the thermostat first.

The heater core can be back flushed with a garden hose. A non-closing thermostat can be identified by pinching the upper radiator hose closed. If the heater gets hot faster that way, replace the thermostat.

Caradiodoc