The answer to 'why is my thermostat blowing hot air' is that there could be several common causes, such as a malfunctioning thermostat, a problem with the HVAC system, or an issue with the wiring. If your thermostat is blowing hot air when it's set to cool, it could indicate that the thermostat is not properly controlling the HVAC system or that the system itself is not functioning correctly.
Some common symptoms of this issue include the thermostat display showing the wrong temperature, the HVAC system running continuously, or the air coming out of the vents being warm instead of cool. Potential solutions may involve adjusting the thermostat settings, checking the HVAC system's components, or troubleshooting the wiring. However, it's important to note that some HVAC issues should be addressed by a professional technician, especially if you're unsure of the root cause or if the problem persists after initial troubleshooting.