1999 Volkswagen Golf AC Heater control

My 99 golf's ac/heater unit is malfunctioning. The only fan setting that works is 4 (max). The ac works however the compressor only turns on in the 1-3 setting. The backlight for the ac button shuts off(as well as the compressor) when moving the dial from 3 to 4 and the cold air that has charged up in the ac escapes into the ducts as the fan blows it out. A side note, the backlights for the entire unti are erratic, and tend to shut off when changing settings