Why do I have to set my passinger side heater to cold to get any heat

This means that there is an issue with the thermostat, or the digital and electronic systems governing the thermostat. Normally, these HVAC systems use coolants to supply heat through heaters and cold air through air conditioning. When one of the components of the HVAC unit fails to work as intended, it can trigger the wrong responses. This commonly happens when certain sensors fail to work as intended and instead, supply heat instead of cold air or vice versa. This can be fixed very easily at an auto-shop or dealership, as it simply entails a replacement of the thermostat. This can also be done at home, with the spare parts being available at any AutoZone.