Does blowing cold air when heater is on mean it is a bad thermostat?

Blowing cold air when the heater is on can indicate several issues, and a faulty thermostat is one possibility. It could also be due to a malfunctioning heater, issues with the ductwork, or low thermostat settings. To determine if the thermostat is the problem, check if it is set to the correct temperature and functioning properly. If the issue persists despite these checks, consulting a professional technician is advisable.