I have a 2004 Silverado Crew Cab, the temperature on the drivers side air vents comes out HOT, all the time, while the passengers side can be controlled by the temperature control lever. If I push the A/C button the air on the drives side is still HOT. Passenger side will come out cold. Any ideas why the drivers side does not work?

I had that problem with my 04. Found out it was the "Blend" door that was bad. After I had it replaced, no more problems.

check the regulator /resistor its the component thats plugged in and mounted at the fan / blower unit this link should help
Replace Blower Motor Resistor in 2004 Silverado

If it has dual zone temp. control it is most likely the heater control panel.

try to pop off the panel to the dash and follow the vent sounds like it has become disconnected somewhere and cold air coming from outside somewhere on firewall also check the heater core see if it is blocked by something like disconnected line

You have a faulty switch. Go to the salvage yard and buy a used one, pull off the trim panel and replace it. I just did one of these last week with the same symptoms.

could be your controller or temp mix door

1. Gain access to the air temperature motor for circuit testing. There are 5 wires at the motor.

2. The Brown wire is ignition power.

3. The Yellow wire is a ground at all times, through the control head.

4. The Light Blue/Black wire carries a 5-volt reference from the control head to the temperature motor.

5. The Light Blue wire is the feedback circuit to the control head and should measure between about 1 volt (cold) and 4 volts (hot). This feedback circuit operates similarly to a Throttle Position Sensor (TPS).

6. The Dark Blue wire is the motor control circuit sent from the control head.

7. When the control head sends out 5 volts on this wire, the motor moves towards hot.

8. When the control head sends out 0 volts, the motor moves towards cold.

9. When the temperature motor reaches the correct position (as measured by the feedback voltage on the Light Blue wire), the control head sends out 2.5 volts. This voltage signals the temperature motor to STOP and hold its present position.

10. Check for correct operation of these voltages.

11. In some cases, the air temperature door doesn't fit correctly in the plenum and will cause the air temperature motor to travel too far. This will cause the control head to become confused and operate erratically.

Check movement of vent doors on that side. Sounds like they aren't moving over as they should. (Or hose fell off on passenger side.)

something fell down defrost vent

check the freon level

i have a 2005 and my # 4 setting on ac doesnt work