Furnace Maintenance

Once a month

Change or clean filters. To determine how dirty the filters are, hold them up. If you can easily see light through them, then they're still clean enough to use.

Inspect the furnace for worn, shiny and sagging belts. They cause undue stress on the fan motor. Repairs require loosening the motor chassis mounts and sliding the motor back enough to make the belt taut and aligned with the fan.

Once a year

Get a yearly preventive maintenance check (about $130) from a service company. At a minimum, the technician should check the fan controls, air filters, blower belt, belt alignment and ducts. He should also check and adjust the burner flame, if necessary.

Cut power 15 minutes before working on a forced-air unit. The blower is a flywheel-type device that spins long after power is off. Also, don't start the unit up until you've screwed the blower back in place.

Vacuum the blower and blower area, and clean blower blades with a brush.

Lubricate the motor with five drops of SAE 20 nondetergent oil. Don't overfill.

Once a year

Get a full checkup (around $130, plus parts) before the start of the heating season. The technician should clean and tune the unit, and inspect, repair or replace as necessary the following: fuel nozzle, oil filter, electrodes, pump strainer and pump gaskets, fuel pump, fuses in the burner circuit, thermostat and transformer. If you're heating forced air with oil, the tune-up should also include a check of the fan controls, air filters and blower belt and ducts.

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