- Check the blower fan is running and relatively quiet. If the fan needs to be replaced, PN NC-1500 (1087/1275) or NC-1520 (859/945)
- Clean the upper section of the NCAT furnace as described in the maintenance section
- Verify the door is closing correctly. See “Door Loose” section
- Check the filter temperature as described in the “Long Burns” section
- Verify there are no obstructions in the exhaust tube
