Heating system only blows out hot air through the vents

I would look at the air blend doors first, it sound like they are not working or your control in the dash is not working send a signal to them. they work by changing the air from hot to cold or in between.

Avalanche, Sierra And Silverado

1. Remove the floor air outlet duct extension (1) from the floor duct (2). Remove the floor air outlet duct extension (1) from the floor duct (2)
2. Disconnect the electrical connection at the blend door actuator (10). Heating system only blows out hot air through the - 0900c152801c9c8b.jpgmages/0900c152801c9c8b.jpg" alt="0900c152801c9c8b.jpg" class="h_mi" />Blend door actuator and related components
3. Remove the blend door actuator mounting screws from the HVAC module.
4. Remove the blend doorHeating system only blows out hot air through the - 0900c152801c9c8c.jpgmbly with the actuator cam. Remove the blend door actuator mounting screws from the HVAC module

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. (1.6Heating system only blows out hot air through the - 0900c152801c9c8b.jpg class="h_mi">Connect the electrical connection at the blend door actuator (10). Blend door actuator and related components
   2. Install the floor air outlet duct extension (1) to the floor air duct (2).
   C/K Series
   
   1. Disconnect the electrical connector to the mode actuator that is located on the left side of the air distribution case.
   2. Remove the screws.
   3. Remove the adjuster links from the control lever.
   4. Remove the mode actuator.
   5. Adjust the mode actuator by completing the following steps:
      1. Connect the electrical connector to the actuator.
      2. Turn the ignition switch to the RUN position. Allow the self-positioning of theHeating system only blows out hot air through the - 0900c152801c9c8d.jpgss="h_mi">Turn the ignition switch to the OFF position.
      3. Remove the actuator from the electrical connection. Blend door actuator-C/K Series
   To install:
   
   1. Install the mode actuator.
   2. Install the screws.
   3. Install the adjuster links to the control lever.
   4. Connect the electrical connector.
   5. Test the circuit operation

Sorry, but after that explanation this may
seem a bit short,but when my car only blows
out hot air, l have the A/C refilled. ??