Thermostat Wiring Diagrams [Wire Installation] Simple Guide Thermostat Wiring Diagrams - Heat pumps are wired for HVAC control far differently than air conditioning systems so make sure you know the difference and correctly identify the type of HVAC system you have installed. Additionally, before you decide to change your thermostat, make sure you have the correct tools especially a screwdriver and wire pliers. Blend Door For Rear HVAC? | GMC Acadia Forum Jan 06, 2017The Aux vents in my '08 Acadia have started blowing only cold air this winter. I figured it was a binding blend door or busted actuator and don't have a service manual to figure out where they all are. I saw over on EnclaveForum a statement that there are four of them: 1) temp for driver 2)..