Half the heater works? I know it's electrical, resistor problems
One of Your mode/blend door actuators is either broken or faulty. Very common problem with these trucks.
http://www.heatertreater.net/videos.html#chevy --- this video might help
Also several other good videos on youtube.
Looking for a Used Silverado 1500 in your area?
CarGurus has 181,204 nationwide Silverado 1500 listings starting at $250.
Search Chevrolet Silverado 1500 Questions
Chevrolet Silverado 1500 Experts
Related Models For Sale
Used Cars For Sale