- Ignitors, whether your furnace uses the electric glow model or a spark-producing unit, only last so long. Eventually all ignitors wear out and require replacement. However, if the furnace receives an improper voltage from your home's electric line, the ignitor will burn out much quicker than normal. A dirty air filter increases the number of times your ignitor switches on and off, shortening its life span. High gas pressure on a gas furnace also produces the same problem.
- Before assuming that your furnace's lack of heat depends solely on a bad ignitor, check the ignitor itself for signs of damage. Preferred Home Repair and Services recommends carefully removing the ignitor and examining it for tiny hairline cracks. The oils on your hands will break the ignitor if it isn't already dead, so wear gloves while examining it. If the ignitor is intact but isn't working, the malfunction comes from another part of the ignition system.
- Homeowners often struggle to see the tiny cracks that stop a modern furnace ignitor from working properly. Connecting the wires of the ignitor to an ohmeter allows you to test the part without removing it from the furnace. If the ignitor returns a reading around 100 ohms instead of 50 or less, it's dead. This ensures that you don't needlessly replace the ignitor or other parts without solving your furnace problem.
- Furnaces over a decade old often don't use electric ignitors at all. These models require manual lighting of the pilot light, but as long as the furnace operates properly the pilot light shouldn't go out. Occasionally a draft or a fuel problem blows out the pilot light and you just need to relight it. Check the furnace before trying to light anything because striking a match near a furnace with a bad ignitor could cause an explosion. A gas furnace fills up with gas when the ignitor fails and this gas ignites easily.
Causes
Troubleshooting
Testing
Pilot Lights
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