Heater blowing hot air on driver side only.

You have actuators which direct the air in the heater/vent/AC system. My first cars used metal cables, then came along vacuum line control and most now use electric control actuators. They control things such as how much air from outside the car come inside, air flow to windshield/floor or dash, control mix of air for temperature adjustment. Your problem more than likely actuator issue. You can try google vehicle year, make, model temperature different from ac vent, when search you can change wording. If vehicle is older and used vacuum lines could have line leak, my 2000 GM van once had vacuum line laying on engine melted line and leaked. My 13 Chrysler, I have changed 2 actuators they are controlled by electric and started clicking when they went bad.

DODGE DART, CHRYSLER 200 CAR BLOWS HOT ON DRIVER SIDE COLD ON PASSENGER OR COLD ON DRIVER SIDE - YouTube

It is most likely that you have a sticking air temperature or blend door that is warped and or the electric actuator motor is defective. When the door warps it usually ruins the little drive motor gearbox.

our honda crv did this , there was a problem with the heater core being partially pluged...there ended up being a recall on heater core

Right blend door actuator failure

There is a module that controls hot/cold direction flow, which does go bad. It's called a Heater Blend Door Actuator, and It's a bear to replace it, but doable. Not too expensive to do it yourself, but you _do_ need to be sure you're buying the exact replacement. You're best bet is to remove it before buying the replacement. The photo of the replacement is all you need to see you're buying the right one. Ford used different models in the same vehicles.

http://www.rockauto.com/en/catalog/ford,2005,freestar,3.9l+v6,1430707,heat+&+air+conditioning,heater+blend+door+actuator,10721

NOTE: LHD model shown. RHD model similar. All vehicles are equipped with a common heater, ventilation and air conditioning (HVAC) housing assembly (1). The heating-A/C system combines A/C, heating, and ventilating capabilities in a single HVAC housing mounted within the passenger compartment behind the instrument panel. The HVAC housing assembly includes:

1. Mode-air doors (2)
2. A/C evaporator (3)
3. Recirculation door actuator (4)
4. Air inlet housing (5)
5. Recirculation-air door (6)
6. Blower motor (7)
7. Blower motor resistor (8)
8. Heater core (9)
9. Air distribution housing (10)
10. Blend-air door (11)
11. Blend door actuator (12
12. Floor distribution ducts (13)
13. Mode door actuator (14)

have an accredited ac shop as an ac cannot produce hot air only cold air so that means that the ac is not working (leaks low on gas etc). The hot air is from the heater in the car and the smell is probably wire overheating or the resistors are burning.

I assume this truck has daul zone heating and a/c, the air blows but is not hot? if this is the case then you may have dissconnected the blend door actuator or it just went bad. this is common that the actuator goes bad,
there are two seperate actuators that control the hot/cold door in the heater box this way the passenger and driver can set there on temp.
the actuator for the drivers side is locted on the drivers side under the dash on heater box, the blower is on the passenger side , you can check connections but i do not think it is that but rather the actuator.

needs gas topping up end of story .

The most likely cause is a failed blend door actuator; however I recommend a little troubleshooting. First, can you hear a clicking sound behind the dash when you turn the setting to hot? If yes, it is certainly the actuator stripping its gears. If not, check to make sure the heater hoses are both hot as they connect to the heater core at the firewall (in the engine compartment). If one or both of the hoses do not get hot, there is a blockage caused either by an air bubble or a stuck water control valve in the heater hose. If the hoses are both hot, the indication is again the blend door actuator.

Below are instructions for replacing the actuator. Look at the diagrams carefully--the big arrows point to the front of the truck and the actuator is on the side of the heater box above the outlet duct that runs to the driver's side of the floor. Also, the actuator is expensive, so I recommend you make sure it's bad and shop around a bit to get a good price. To check out the actuator, first see if you can turn the blend door by hand. If you can't turn it, maybe it's jammed. Also, reconnect the actuator after removing it and see what it does when you turn the heater to hot.

Removal & Installation

1. Remove the floor air outlet duct extension (1) from the floor duct (2).
   

   

Fig. Remove the floor air outlet duct extension (1) from the floor duct (2)

Disconnect the electrical connection at the blend door actuator (#10 in pic below).

Fig. Blend door actuator and related components

Remove the blend door actuator mounting screws from the HVAC module.

Remove the blend door actuator as an assembly with the actuator cam.

Fig. Remove the blend door actuator mounting screws from the HVAC module

To install:

1. Install the blend door actuator as an assembly with the actuator cam.
   1. Line up the heater/defroster valve lever with the blend door actuator cam slot.
   2. Line up the A/C valve lever with the blend door actuator cam
   
   
2. Install the blend door actuator mounting screw to the HVAC module.
   1. Tighten the blend door actuator mounting screw to 14 inch lbs. (1.6 Nm).
   
   
3. Connect the electrical connection at the blend door actuator (10).
4. Install the floor air outlet duct extension (1) to the floor air duct (2).

Picture of actuator: