Lennox Furnace Problems

The chances are high that you would have to deal with quite a few furnace-related problems during the unit’s lifespan. 

The most common Lennox furnace issues include dirty filters, mechanical wear and tear, pilot and ignition control issues, strange noises, and issues with the thermostat. Fortunately, the majority of these problems can be avoided with proper and regular maintenance and care. 

What Is the Most Common Problem with Furnaces?

If you are a proud furnace owner, you might agree that it is challenging to pick the most common issue when it comes to Lenox furnace problems. So, here is a list of the most widespread issues that you might encounter at one point or another.

Clogged or Dirty Air Filters

A lot of furnace problems can be fixed by replacing an old filter with a new one.

A dirty filter makes your unit work harder which might cause the furnace to wear out much faster, overheat, or even break down. A clogged air filter also worsens the quality of the air in your house and it can make your energy bills skyrocket.

Consult an HVAC expert to choose the air filter that is the best fit for your Lennox furnace and change the component on a regular basis.

Read: Why Does My Furnace Filter Get Dirty So Quickly

Mechanical Wear and Tear

Over the years, some parts of the furnace are going to wear down.

The actual unit might last you over 15 years, while such components as the flame sensor and the thermocouple, for example, would have to be changed every few years.

That’s exactly why you can’t underestimate the importance of annual maintenance. A professional is going to check every part of the heating system, replace the parts that have worn down, and take care of the other components to increase the overall life span of the unit.

Read: Furnace Flame Sensor – Troubleshooting Guide

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Pilot or Ignition Control Issues

Gas furnaces have either a pilot light or an electric ignitor. One of the most annoying, but, unfortunately, common issues, is a flame that won’t stay lit.

You might have to clean the flame sensor or the pilot orifice, in such a case. 

Luckily, annual check-ups will help prevent these issues as well.

Issues with the Thermostat

If there is something wrong with your thermostat, the heating system won’t be working efficiently or will fail to even turn on.

Sometimes, homeowners accidentally switch their thermostats to ‘cool’, instead of ‘heat’. So, make sure to check that.

At times, you might simply need to change the device’s batteries to make it work again.

Finally, make sure that you have chosen the right location for your thermostat. It has to be out of direct sunlight and any other sources of heat.

Read: Why Does Home Thermostat Say HEAT ON But There Is No Heat?

Strange Sounds

If your furnace started making noises that it normally doesn’t, then it is certainly something that you should pay attention to.

Scraping and grinding sounds can mean that the bearings are dry (during the check-ups, professionals should lubricate them). A rumbling sound can indicate a problem with the burners, pilot light, or flame sensor.

A squealing sound means that there is something wrong with the blower motor, while a humming sound that is louder than normal might be an indication of an issue with the capacitor or fan.

Read: Furnace Noise Problems

What Does a Red Blinking Light on a Lennox Furnace Mean?

LED lights and error codes are how a Lennox furnace can communicate with you.

Usually, the units have two lights. If they are both flashing slowly, then everything is okay; if they are flashing fast, then there is a call for heat (which is normal as well).

However, other signals might indicate that there is something wrong with your furnace.

If one light is blinking slowly and the other one – rapidly, then it looks like the system is experiencing a low flame issue, a reverse polarity, low voltage, or a short circuit. 

All Lennox furnaces come with special instructions where you can find out what each code means. 

Read: Lennox Furnace Error Codes – Troubleshooting Guide

How to Check Pilot Light on Lennox Furnace?

To check if your pilot light is out or not, you would have to open the front cover panel on the furnace. If there is a little flame, you are going to see it. 

Tip: while you’re looking at the pilot light, make sure to pay attention to the color of the flame – it should be blue. If the flame has a strange color, then the burner assembly might need cleaning.

Do bear in mind that you can manually ignite the pilot light only in the Lennox furnaces that have an automatic gas valve and standing (constant) pilot flame.

Gas furnaces with an intermittent pilot (‘X’ and ‘E’ series) have a pilot ignitor and you should not attempt to light the flame yourself.

Before lighting a standing pilot, always make sure to smell around the appliance. Do smell next to the floor as well, as some gas will settle there (it is heavier than air).

If you have detected a gas smell, call the National Gas Emergency Service and evacuate everyone from the house.

Read: Why Lennox Furnace Not Igniting?

Lennox Furnace Control Board Troubleshooting

In the majority of cases, experts will replace the control board, only if nothing else had helped get your furnace to operate correctly again.

If there are interruptions in the normal sequencing of your unit and the temperature is unstable (the thermostat and all the other components are okay), then a bad control board might be the issue.

Before proceeding any further, make sure to check the LED lights and consult the manual. Some codes can be linked to the control board.

For example, the code that indicates ‘low voltage’ suggests that there is something wrong with the control board.

Follow these steps only if you feel comfortable working with electricity and a voltmeter. Bear in mind that the furnace will remain ON during this inspection as you will be testing whether the electricity is flowing correctly or not.

  1. Remove the access panels (one houses the actual control panel, while the second one – other furnace components).
  2. You can use electrical tape to keep the door switch down while you’re performing the test. This will keep the electricity running in the furnace.
  3. Usually, you will find the control board in front of the blower. It has a lot of wires running in and out.
  4. You would have to confirm that power is getting to the board. If there is an indicator light, simply see if it’s on or not.
  5. If there is no indicator light, then touch the metal connector of the line voltage and the common wire with a voltmeter (it should show 120 volts). The common wire is usually labeled COM on the transformer and the line voltage is labeled LINE on the control board.
  6. Touch the high voltage and the low voltage wires on the transformer (the voltmeter has to show 120 V and 24 V respectively). The transformer is a rectangular box with 4 wires; the high voltage wires are the black and white ones.
  7. The two low voltage wires connect to a Molex plug. Place the meter leads into the sockets – you should see 24 volts.
  8. At the edge of the control board, you’ll see the terminal strip. There are 5 wires, touch the R and the C wire (the voltmeter should show 24 V).

If all the readings were correct, then your control board is working properly and there is no need for replacement. 

What Is the Life Expectancy of a Lennox Furnace?

According to Lennox, their furnaces have a lifespan of around 15-20 years.

The experts recommend replacing your unit, if:

  • The furnace is getting close to the end of its lifespan
  • You have spent over $5.000 on various furnace-related repairs
  • You are inviting your HVAC technician over a bit too often
  • Your furnace is not ENERGY STAR qualified
  • Your system is not sized correctly