Problem: Furnace will not ignite the gas to produce heat for your home. The furnace hot surface ignitor does not glow. When a furnace has a bad ignitor. This is what I see in the furnace sequence of operation:
1. Thermostat calls for heat.
2. Draft inducer motor starts.
3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. You might smell some gas. The ignitor did not glow, the flame sensor (a small metal probe about 1/8″ in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas.
Solution: You probably need to purchase and install a new ignitor.
- We sell furnace hot surface ignitors on the following page: Please Click Here to see the name brand Furnace Ignitors we sell. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you touch an ignitor with your hands the oil off your skin can transfer to the ignitor and shorten the life of the ignitor. Below we have a picture showing a cracked ignitor.
- If you do not visually see a crack in the ignitor, then I would suggest that you unplug the ignitor and take an ohm meter reading to see if the ignitor is burnt out. Set the multimeter so it can properly measure a resistance of 10 to 200 ohms. Disconnect the hot surface ignitor from the control board and measure the resistance. A good hot surface ignitor will have a resistance of 40 to 90 ohms. Greater than 90 ohms indicates a failing or failed hot surface ignitor.
- We have two YouTube videos below that show hot to test and troubleshoot furnace ignitor problems.
- If your ignitor tests OK with an ohm meter, then you could have a furnace control board problem or you could have an open limit or rollout switch problem. We sell furnace limits on the following page: Please click here to go to our furnace limits and rollouts page.
- The furnace’s control board might not be supplying the voltage to the ignitor. Please click here to see our Furnace Control Boards Page.
- If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you can try to clean your flame sensor with light sand paper (emery cloth) or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning. Please see the pictures below to help identify the difference between a flame sensor and a furnace hot surface ignitor. If you need a new furnace flame sensor then we sell furnace flame sensor on the following page: Furnace Flame Sensors Page.
- Please send us your furnace’s model number if you would like for us to recommend a furnace part. On Rheem Ruud furnaces we will need both model number and serial number. On Bryant Carrier furnaces we will need the product number. Our email address is: firstname.lastname@example.org. We try our best to answer all emails as soon as possible. Usually within one hour during normal business hours. 7 AM. – 4 PM. Eastern Time.
- We would love to help you out and have your business!
Below are pictures to help you identify the difference in a flame sensor and a hot surface ignitor. On the top we have pictures of three different types of flame sensors. On the bottom is a picture of a hot surface ignitor. Please make sure you do not touch the gray glass part of the ignitor. If you do it can shorten the hot surface ignitor’s life.
Below we have a picture of a hot surface ignitor:
Below we have two YouTube videos that explain how to troubleshoot furnace ignitor problems. The top YouTube Video shows how to replace your furnace ignitor and flame sensor:
The YouTube Video below shows you how to test a furnace hot surface ignitor. We hope this will help you troubleshoot and repair your furnace.