Oil-Furnace Troubleshooting

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Are things in your basement not going bump in the night? When your oil furnace quits, try some diagnosis before before calling a professional.

On the whole, oil furnaces are considered to be among the most durable household appliances. Even though many manufacturers claim that their units have only a 10-year usable life, a homeowner can often expect 15 to 20 years of service from a properly maintained furnace.

However, this is not to imply that an oil burner won't develop a few ailments now and then, typically on the coldest night of the winter. In some instances, only a minor repair or adjustment will be required, but in many cases, you'll need the services of a qualified heating professional to restore the furnace to good health. Even so, if you're familiar with common problems that oil burners develop and their recommended repairs, you'll be better able to judge the quality of a repairperson's work and ward off the incompetent or unscrupulous.

In the discussion that follows, former EcoVillage Director Leroy Richter, who teaches a popular introductory course on furnace repair at a local technical institute, lists some common oil furnace problems and some ways to correctly diagnose the trouble.

[1] The furnace won't start.

First of all, Leroy advises, press the reset button, which manually starts the furnace. It's located either on the primary control at the stack (on older models) or on the burner motor (on newer appliances). Push the button once or twice; however, if the furnace doesn't come on and stay on within 60 seconds, stop pushing the button and check the fuses or circuit breaker. Don't keep pushing the reset button, which merely loads more fuel into the combustion chamber. If you do and the furnace finally does fire, you'll have a "heck of a lot of oil" in there, Richter points out.

Sometimes the motor on the burner assembly will burn out, Leroy says. If this is the case, the motor will have to be replaced. Over-oiling the motor, which is sealed, is probably the most common cause of failure. Another possibility, though a rare one, is a faulty starting switch on the motor, which is an inexpensive repair.

[2] The burner is running but there's no fire.

In this case, turn your attention first to the burner nozzle. "The opening in a nozzle is smaller than the tip of a needle," Richter points out, "and the slightest amount of water or trash can clog it up." If it's been a while since you changed the nozzle, replace this inexpensive part and see if the furnace will now operate properly.

To check for water, disconnect the oil supply line from the burner assembly and catch the fuel in a clean jar. Hold it to the light and look for the presence of water. A homeowner can minimize fuel contamination by following these suggestions: [A] Shut the furnace off while oil is being pumped into the tank and then leave it off for another hour until any trash that's present has a chance to settle in the bottom of the tank. [B] Have the oil deliveryperson check for excess water in the tank by using a simple test, a squirt of water-sensitive paste on a long stick; if water is present, drain the tank and check for cracks. [C] Keep the tank topped off with fuel, a practice that won't disturb the bottom sediment as much as infrequent fill-ups will.