If the windows will not defrost what is the problem?

If the Windows will not defrost, it could be due to a faulty heating system, such as a malfunctioning heater core or blower motor. Additionally, low coolant levels or a clogged cabin air filter can impede proper airflow and heating. It's also possible that the defrost setting isn't activated or functioning correctly. Ensuring the vehicle's ventilation system is set to the defrost mode is essential for effective defrosting.