2004 Chevrolet sliverado air conditioning blowing hot air on front passenger side
It sounds like the directional sw (upper,lower,defrost etc) is leaking vacuum .... before you tear into the mixer door and vacuum actuator under the dash ... check that rotary switch. It's a combo electro-vacuum switch and the "O" rings fail ... the switch won't go the the correct position.
It's probably the blend valve actuator below the dash. I just had the same problem with my 2011 Silverado on the driver side. I bought a new one off Amazon for $65.
Search Chevrolet Silverado 1500 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet Silverado 1500 Experts