Completed heating tune up, gave an estimate for a blower wheel cleaning due to dirtiness. Homeowner also stated that their system began freezing yesterday & today. Checked pressures/temperatures after completing heating tune up & everything checked out fine, cause of freezing was a dirty filter. Replaced it with a 2” filter. Recommended keeping up with filter changes to prevent it from happening again. No other issues to report. Placed yard sign & filled out comfort survey.