Signs of a Bad Thermostat in House: Inconsistent or inaccurate temperature control, indicating a malfunctioning temperature sensor or faulty electrical connections. Incorrect temperature readings, suggesting a broken thermometer or a problem with the thermostat’s display. Excessive or frequent cycling of the HVAC system, pointing to a thermostat that is not properly regulating temperature. Variations in temperature between different rooms, hinting at issues with thermostat placement or a faulty HVAC system.