Technical Description (Comment)
WARNING: This page is about a different car, the 2015 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.
The wiring harness wire or connectors may have loose, corroded, or damage terminals, or terminals pushed back in the connector, or the A/C controller assembly (A/C-ECU) or heater controller assembly (A/C-ECU) (vehicles without A/C) may be defective.