I have little heat in my 2004 Buick Lasaber ,it has a 3800 series 2 engine and electronic climate control. what could cause this?

Stuck thermostat.

Stuck thermostat.

First thing tried put in new one,there is a bleeder on the thermostat houseing could that be the problem?

Clogged heater core. Back flush the core.

Reverse flush the heater core. Check the blend door operation, if the problem persists--there may be a problem with the blend door actuator.