Lennox Furnace Repair Guide
Troubleshooting, Error Codes & More
(Updated for 2019)
A complete Lennox furnace repair guide, from how to replace your air filter, to troubleshooting and error codes, model numbers and more!
Please note, the following is for informational purposes only. Any servicing you attempt is at your own risk.
Lennox International has been a household name for well over a century, and the company has been a revolutionary leader in the HVAC industry ever since its inception back in 1895. Today, they’re known for making high-quality oil and gas furnaces, including budget-friendly ones, high-efficiency models, and low-emissions furnaces as well.
If you’re one of the many Canadians who have a Lennox furnace keeping your house warm, this quick guide will tell you what you need to know about regular maintenance, getting help from a technician when you need it, and getting the most life out of your heating system.
How to Replace Your Air Filter
Furnace filters filter the air being drawn into your heating system, meaning they improve air quality, increase the efficiency of your furnace, and keep contaminants, pollutants, and allergens out of the air. To work effectively, the filters have to be changed every one to three months during the heating season, and here’s how you do that:
- Check your owner’s manual to find out what kind of replacement filter you need for your particular Lennox furnace model.
- When you have the new filter, remove the access panel from the furnace (or slide it open) to get to the filter.
- Slide out the old filter.
- Find the arrows on the new filter and use them as a guide for inserting it, and then slide it into place.
- Close or replace the access panel.
What’s Wrong With Your Lennox Furnace?
Remember to always turn your furnace completely off before opening it up to look around or attempt any fix.
|Is your furnace...||The problem might be your...||What's wrong?||How you can fix it:|
|Not heating?||Circuit Breaker/Fuse||Most likely, either the electrical system providing your furnace’s power has shorted or the power switch has blown.||Try resetting your furnace’s circuit breaker. If it has blown, you will need to replace it.|
|Igniter||The furnace’s igniter might either be cracked or faulty.||Check the part for cracks, if it is then replace the igniter. If it isn’t cracked, use a multimeter to test for continuity.|
|Cycling irregularly?||Thermostat||Your thermostat might be adjusting incorrectly, causing the furnace to cycle on and off too often.||If your thermostat has an adjustable calibration scale, adjust the heat anticipator. If this does not stabilize the unit, you may have to replace the thermostat.|
|Not blowing hot air?||Blower Motor||Your blower motor may have completely burnt out. If this doesn’t seem to be the case, then the connecting belt may have simply broken.||Test to see if power is reaching the motor. If it does, but isn’t running, the motor has likely failed. If the motor runs but air doesn’t move, the connecting belt has probably broken. You’ll have to replace the belt.|
|Blowing too much air?||Control Board||The control board regulates the amount of voltage that reaches each functioning part. If the relay that controls the blower motor has failed, it will continually send voltage to the motor.||Replace the control board.|
|Thermostat||The contact that controls the blower motor on your thermostat may be stuck closed, causing the blower motor to run continuously.||Use a multimeter to check for continuity. If it appears the thermostat is the issue, replace it.|
|Leaking water?||Drain Pipe|
|Starting and then stopping shortly after?||Flame Sensor||Your furnace’s flame sensor monitors the burner, detecting whether a flame is present. If it is either defective or dirty, it will not be able to detect a flame.||If dirty, clean the sensor using a fine abrasive pad. If faulty, replace the flame sensor.|
Lennox Furnace Error Codes
Lennox furnaces are equipped with two LED lights that will flash in different patterns to help you diagnose various problems. If both LEDs are flashing together slowly, it means the furnace is operating normally. If both are flashing together quickly, it means the operation is normal, and there’s been a call for heat.
Here’s a list of error codes you might encounter:
|Lennox Error Code||What this means|
|LED 1-slow flashing; LED 2-continuous||The high limit switch is open.|
|LED 1-slow flashing; LED 2-off||There was a flame detected with no gas.|
|LED 1-off; LED 2-slow flashing||Draft inducer is not operating or the pressure switch circuit has closed.|
|LED 1 & 2-alternating, slow flashing||There's been a flame failure.|
|LED 1 & 2-alternating, quick flashing||The furnace does not have enough voltage.|
|LED 1-slow flashing; LED 2-fast flashing||The flame is low.|
|LED 1-fast flashing; LED 2-slow flashing||The furnaces polarity is reversed.|
When Should You Call A Professional?
Not all furnace repair and maintenance issues require the help of a certified technician, but some do, including if your Lennox furnace:
- Is making noises, including squealing, rattling, and whistling, which are often caused by a mechanical problem
- Has cracks in it
- Is leaking or has water pooling on the floor around it
- Isn’t blowing hot air or isn’t producing any heat
- Is emitting a gas odour
- Has a problem with the heat exchanger
- Is blowing cold air and the thermostat isn’t the cause
- Won’t stay on because the flame sensor needs to be replaced
Who Should You Call?
Finding a certified HVAC company that you like and trust can be hard to do.
For one thing, there’s a lot of information and terminology you need to know to be able to speak the same language as a technician, and this can make it hard to understand furnace problems, diagnoses, and solutions. To make the process of finding the right technician easier, we’ve created an independent HVAC contractor certification program you can use to find a company in your area that you can rely on.
Lennox’s Warranty Coverage
All Lennox furnaces come with parts and heat exchanger warranty, and the model of your furnace will determine how long the warranty lasts.
- Dave Lennox Signature Collection series: Furnaces in this series have a 10-year warranty on covered components and a 20-year warranty on the heat exchanger.
- Elite series and Lennox Merit series: These models have a five-year warranty on covered components and a 20-year heat exchanger warranty.
Extended limited warranty: If you register your furnace after installation, you’re eligible for the extended warranty. This extends the five-year component’s warranty on Elite and Lennox Merit furnaces to 10 years and extends the 20-year heat exchanger warranty to a limited lifetime warranty for certain models in the Lennox Merit series.
Lennox Model Numbers
Current Lennox Models
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