The answer to 'thermostat smells bad' is that a smelly thermostat is often caused by a buildup of dust, dirt, or debris inside the unit. This can lead to a musty or unpleasant odor. The most common symptoms are a noticeable smell coming from the thermostat, and potentially reduced air quality in the home.
To resolve this issue, you can try cleaning the thermostat yourself. First, turn off power to the thermostat at the circuit breaker. Then, use a soft brush or cloth to gently wipe down the exterior of the unit, being careful not to damage any internal components. You can also use a can of compressed air to blow out any dust or debris. If the smell persists after cleaning, it may be necessary to have a professional HVAC technician inspect and service the thermostat.