I have a 2004 monte carlo and my driver side heat does not work it blows out cold air even when the control switch is on the heat my passenger side works fine

check the actuator motor and make sure it is moving the doors between the heater and the ac. it is in the center of the heater inside the car and is a small motor attached to the heater housing.

your vehicle has 2 heat sensors I am gathering with 2 fans 1 of the relays is bad most likely ..autozone reads this free and will take out the guessing game

Your heat cold damper is not closing. Actuator could be sticking or bad. Or some of the foam has come loose on the damper seal. Have seen leaves in the system causing obstruction. The problem is most vehicles require dash removal to fix the problem.

you have "blend doors" under the dash, most likely you have dual side temp controls, and the little electric blend door actuator is bad, they are not easy to get to, but can be done in the drive way, hope this helps,

Hello, this is cused by the drivers side temp door actuator. there are two electric motors that move the temp doors from cold to hot. there is one on the drivers side and one on the passenger side. you will need to replace the one for the drivers side.

Remove the left instrument panel (I/P) insulator.

Remove the knee bolster bracket bracket. Disconnect the electrical connector from the left air temperature actuator.

Remove the mounting screws from the left air temperature actuator.

Remove the left air temperature actuator.

a little tip is to "vent" the topmost hot hose whith the engine running to clear any trapped air in system.....loosen the clip,whilst under pressure,wear rubber bloves cos it bloody hot.......

dual climate controls are freon sensitive , be sure
your system is fully charged.

Sounsds like the HVAC is dual system, and the door motors have failed, try swapping the door motors with the door motors that work on the passenger side.
If they work, the control head may be the issue, try and test the output of the control head, see if there is a signal to the motors, getting a wiring schematic will help in this matter.

your coolant level is low and an air pocket has therefore settled in the driver's heater core. if it doesn't appear low on the reservoir then you should have the system drained and refilled properly to evacuate the air pocket that is causing the cold air on the driver side.

Hello. The side that is not operating properly has a bad temp door actuator located up under the dash. I am assuming this vehicle has driver/passenger(dual)climate control heat and cold settings. This is a very common problem on these vehicles. Hope you find this information useful!