The answer to 'why is my thermostat smells bad' is that a smelly thermostat is often caused by dust, dirt, or debris buildup inside the unit. This can lead to the growth of mold, mildew, or bacteria, which can produce unpleasant odors. Other common causes include spills or leaks near the thermostat, or the use of certain cleaning products that leave behind a chemical smell.
If your thermostat is giving off a bad smell, it's important to address the issue promptly to prevent the problem from getting worse. You can try cleaning the thermostat yourself by gently wiping down the exterior with a damp cloth, but if the odor persists or you suspect the issue is more serious, it's best to call in a professional HVAC technician to inspect and properly clean the unit.