How do you diagnose oil furnace ignition problems?

Furnace ignition problems have several possible causes. To diagnose such a problem you need a flashlight, a screwdriver, heavy work gloves and a mirror with an angled handle. The length of time necessary to identify the problem varies according to the age and location of the furnace.

1. Verify the power supply

   Locate the furnace's power switch, and verify that it is in the "on" position. Check all visible power cables for damage and loose connections.

2. Remove the covers, and look for spilled oil

   Don your work gloves, and remove the furnace's access panel. Inspect the interior for spilled oil. Inhale deeply, and make note of unusual smells, especially the odors of fresh oil and burned oil. If you smell unburned oil and do not find leaks, your furnace probably has an ignition problem.

3. Reset the furnace

   Reset the furnace, and attempt to ignite it.

4. Inspect the combustion chamber

   Use a mirror with an angled handle to look inside the combustion chamber. If it's full of unburned oil, do not try to light the furnace again. Seek professional help. If the chamber is not flooded with unburned oil and the furnace motor is operational, continue troubleshooting.

5. Examine the combustion chamber

   Turn the furnace off, and open the combustion chamber inspection flap. If the chamber contains oil droplets, examine the furnace's transformer, which is the small box on top of the burner.

6. Test the transformer

   Turn the burner on, and touch one of the transformer's terminals with a screwdriver. Pull the head of the screwdriver back and look for a spark. A weak or non-existent spark indicates possible transformer failure.

7. Clean the insulators

   Clean the insulators below the transformer's terminals, and repeat the spark test. If the spark remains weak or absent, your furnace needs a new transformer. Seek professional help.