Abstract: An electronic climate control system is provided for controlling an HVAC system on a bus or other high-occupancy vehicle either as a stand-alone system or for retrofitting with existing HVAC equipment. The system includes a system control unit having output terminals connected to the vehicle compressor, condenser and evaporator units for control thereof, as well as a user control unit electrically coupled to the system control unit for receiving user inputs. The user control unit includes one or two switches, each sized to fit with an adaptable housing into standard rocker switch blanks of varying sizes in a bus control panel. These highly integrated switches, which are programmable and can support system control units of varying complexity, are easy to install and use, and provide multi-function capability including dynamic temperature and diagnostic outputs.