I have a rental property that set empty for a year. My renters just moved in today and tonight the heater started blowing cold air. It was working fine this morning. They said the pilot is lit and no breakers are thrown. Could a really dirty filter cause this problem? Any other ideas?

Thanks, Darin

Yes it could. Most modern furnaces are designed to run a continuous blower if they overheat and trip a limit control. A clogged air filter will starve the system of airflow and could very well cause the problem you are experiencing.