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Why Is My Lennox Furnace Blinking Red? (Read This First!)

There may be a problem with your Lennox furnace if you see red blinking red lights. In case you’re not sure what the problem is, or if you just want to make sure it’s handled quickly and efficiently. Here are some guidelines for you. 

Let’s find out why your Lennox furnace is blinking red.

Lennox furnace blinking red light

The red lights on your Lennox furnace may be blinking for several reasons. This indicates a problem with the thermostat or control unit of the furnace. Gas valves, fuel supplies, or igniter controls may also contribute to this problem. Lennox furnaces occasionally blink red if the heat pump fails.

To determine the cause of your blinking red Lennox furnace light, a qualified technician needs to access the unit. Alternatively, you can check what causes the issue manually. There are a few common reasons why a Lennox furnace may blink red lights.

Problematic Thermostat:

The thermostat is the most common cause of a blinking red light on a Lennox furnace. It could be caused by faulty parts or malfunctioning sensors. The thermostat will need to be replaced if the problem is with cooling or heating.

Problematic Control Unit:

Another reason why your Lennox furnace may be blinking red lights is a faulty control unit. The unit may face this problem if it has been damaged by water or if its electrical connections have been damaged. 

The control unit must be replaced before repairs or replacements can be performed.

Gas Valve issue:

Your Lennox furnace may have a malfunctioning gas valve if the red light is blinking. The valve itself can be corroded or clogged with debris. Replacement of the gas valve will be required to resolve this issue.

Heat Pump not working:

The red blinking light on your Lennox furnace is likely to indicate that the heat pump has stopped working if you notice that there is no heat being produced. 

It will be necessary for a technician to access and test all of the associated components to troubleshoot and repair this problem.

Blocked HVAC Filter:

Your Lennox furnace may be blinking red due to a blocked HVAC filter if the light is coming from the blower fan. Often, this is caused by dust or debris building up inside the unit. Replacement of the HVAC filter is the only solution to this problem.

Problematic igniter control:

Your Lennox furnace may be malfunctioning if the red blinking light on the igniter control is coming from there. The control unit may be clogged with debris or corrosion. An igniter control replacement will be necessary to fix this issue.

Why is my Lennox furnace is blinking red and green?

There are a few reasons why your Lennox furnace may be blinking red and green. Defective electrical connections, water damage, and faulty gas valves are the most common culprits. You may need to replace your thermostat or motor in some cases. 

A blinking red light may also indicate a blocked HVAC filter if it’s coming from the blower fan.

Nevertheless, this is a very small percentage of cases. Most often, a blinking red light indicates that one or more internal components are malfunctioning.

You should schedule an appointment with a professional technician if you notice any other problems with your Lennox furnace. The issue will be diagnosed and fixed quickly and efficiently by them.

What does a blinking red light mean on a Lennox furnace?

A blinking red light on a Lennox furnace indicates that one or more of its internal components are malfunctioning. Defective electrical connections, water damage, or faulty gas valves could cause this problem.

2 times:

Blinking red twice means blowing cold air. There is a good chance that this is happening because the furnace is not able to catch a flame. It is possible to solve this problem by turning the knob of the heater so that it heats up faster.

3 times:

Flashing red lights in Lennox furnaces three times in a row indicates that the combustion air pressure switch monitoring airflow through the vent system failed to close while the induced draft motor was running.

4 times:

When the Lennox furnace blinks red four times, it indicates that the temperature has reached an unsafe level. Furthermore, it indicates that a 24-volt fuse is blown or that the high-limit switch is open.

5 times:

A flashing red light on a Lennox furnace indicates it has detected a flame without requesting heat. One of two things usually causes this: A malfunctioning pilot light. You may have a problem with your air filter or with the igniter (heat element). 

It appears that one of the sensors inside has failed.

6 times:

Six blinks in a row on a Lennox furnace indicate that the voltage polarity has been switched. To resolve the issue, you must have your voltages restored by a professional.

7 times:

Your Lennox furnace’s burner tube may have failed if you see an unrelenting blinking red light. In addition, there is an error related to low flame. You can fix this by checking the igniter for continuity. 

The red light will continue blinking even when there is airflow through the furnace if there is a break in it.

8 times:

When you see a flashing red light on your Lennox furnace 8 times, it’s most likely caused by a power outage. Your furnace needs power from both the electric box and gas valve to operate during an outage. 

A failure of either of those sources will prevent your unit from turning on or staying on.

9 times:

It’s probably time to call a professional if your Lennox furnace blinks red nine times in a row. When this error occurs, there is usually a problem with the control board or another significant component.

10 times:

When your Lennox furnace shows 10 times blinking red light, that means the heat isn’t reaching the burner tubes. There are a variety of reasons that can cause this, but most likely one or more tubes have been damaged.

How do you fix a blinking Lennox furnace?

Power outages often cause Lennox furnaces to blink, so restore power by reconnecting the electric box and gas valve. It is necessary to call a professional if the problem is related to the control board or other components inside the unit. 

Here are the steps you can follow to fix the issue on your own.

Make sure you have the correct tools:

It is very important to have the right tools on hand before starting any repair work on your vehicle. The first thing that you will need is a multimeter to check for continuity and a Phillips head screwdriver to make some basic adjustments.

Check the igniter for continuity:

The first step is to examine the igniter for any damage. A break will cause the red light to come on and continue blinking even when the furnace is operating.

Test each burner tube using your multimeter:

If the igniter is not the cause of your blinking furnace, you will need to test each burner tube. First of all, you will need to disconnect one end of each tube and plug it into a working electrical outlet to do this. 

Using your multimeter, you can then check to see if there is continuity between both ends. The red light will come on if there is a break in the wire, and it will continue to blink even if there is airflow through the furnace when there is a break in the wire.

Replace any damaged tubes:

You will need to replace one or more of the burner tubes if there is a break in one or more of them. The first thing you need to do to do this is to remove the cover of the furnace by removing the four screws on either side of it. 

Using your Phillips screwdriver, you will then be able to unscrew each burner tube and slide it out of its mount as you do so.

Select the appropriate replacement tubes and screws:

You will need to select an appropriate replacement burner tube and screw from your stock once you have determined that one or more of the burner tubes is damaged.

Additional tips:

After replacing the tubes and the screw, if the furnace is still blinking after replacing tubes and the screw, it may be necessary to replace the control board of the furnace. As a first step, you need to remove two screws on each side of the control panel to slide it out of the way.

Final Thoughts

In conclusion, the Lennox furnace may be blinking red light due to a faulty igniter, a defective burner tube, or a malfunctioning control board. To rectify the problem of a blinking red light, test each burner tube and replace any damaged parts if necessary.