Annual service checklist

What is going on

What I usually find on a furnace that has not been looked at in a few years is a dirty blower wheel, a plugged filter and a slightly loose connection somewhere. This is the checklist for the start of each heating season, and most of it is quick. The blower motors are prelubricated, so do not oil them. Filters live outside the unit and are field supplied, so they are yours to watch monthly.

Likely causes

• Dirty blower wheel cutting airflow
• Plugged filter causing high temperature rise and limit trips
• Vent pipes blocked by snow, ice or frozen fog
• Loose wiring connections causing intermittent faults
• Supply voltage out of range or high blower amp draw

Check in this order

1. Check the blower wheel for debris and clean it if needed. Blower motors are prelubricated and need no oil.
2. Inspect filters monthly and clean or replace them as needed. Filters are field supplied and mounted outside the unit.
3. Check exhaust and air intake pipes and connections for tightness and blockage.
4. After heavy snow, ice or frozen fog, clear snow or ice from the plastic intake and exhaust pipes.
5. Check all wiring for loose connections with power off.
6. Check furnace supply voltage (120 VAC ±10%) and blower amp draw with a meter.
7. Turn the power back on, run a full cycle and listen for anything unusual.

More furnace guides

• Annual planned service inspection
• Blower access panel and carbon monoxide hazard
• Burner assembly cleaning
• Change blower speed tap
• Check temperature rise and adjust blower speed
• Check venting and combustion air on non-direct vent installs