2003-2004, 2006 Chevrolet Trailblazer EXT 5.3L V8. 2002-2006 Chevrolet Trailblazer EXT 4.2L 6 Cyl. Notes: HVAC Pressure Switch -- High Side Refrigerant Press; Three Wire. In earlier vehicles, they are used to directly turn the compressor off to avoid compressor failure.
