Performed annual heating maintenance Lincoln. 19 yr old York split Attis yard. Found system tstat without batteries. Turned system on, found filter dirty, 20-24-1. Recommend changing filter more often. Or switching to a washable electrostatic lifetime filter. Unit appears to have repairs done in the past. Checked hot surface ignitor ok, checked blower capacitor ok. Ran system, system running at this time. Turned system off. Come summer need to dive more in-depth on drain pan, and drain lines.