Keeping a furnace in excellent condition isn’t always an easy task because of all the mechanical and electrical components. Despite Lennox Furnaces’ stellar reputation for dependability and efficiency, problems can arise with any complicated piece of equipment that is used in your home. In this article, we have listed some of the most typical issues with Lennox furnaces, along with detailed but easy instructions for fixing them.

Common Lennox Furnace Problems and Solutions

A number of factors, from a faulty thermostat to more complex issues connected with the gas supply or burners, could be causing your Lennox furnace to either not heat up or blast cooling or chill air.

Troubleshooting Steps:

  • Power Check: Make sure the power is going to your furnace before anything else. Verify that the furnace switch is turned on and that no circuit breakers or fuses have blown.

  • Thermostat Settings: Adjust the thermostat to "heat" rather than "cool" and select "auto" mode instead of "on," which will keep the fan running all the time regardless of the temperature.

  • Temperature Setting: To test if the furnace turns on, raise the temperature setting on the thermostat and hold it there for a few seconds. On occasion, the furnace won't turn on since the set point is lower than the actual temperature in the house.

  • Check the Air Filter: If the air filter is dirty, the airflow will be restricted, which can lead to the furnace overheating and turning off or blowing chilly air. To fix a blocked filter, simply replace it.

  • Gas Supply: The gas supply to the furnace must be open, therefore make sure you check that valve. It is imperative that you contact a professional without delay in the event that you detect the odor of gas or suspect a leak.

More wear and tear, higher energy costs, and inefficient heating might result from a constantly running furnace.

Troubleshooting Steps:

  • Thermostat Check: It goes without saying that you should check the thermostat to make sure it is set to "auto" rather than "on." You should also make sure the thermostat is giving you the right readings. If you're still unsure, try a different thermostat or fresh batteries.

  • Filter Replacement: The furnace may operate more than necessary to achieve the desired temperature if the filter is unclean, thus it's important to change it often. If necessary, get a new one.

  • Ductwork and Air Leaks: Check for air leaks and draughts in the ductwork of your home, paying special attention to the areas surrounding the doors and windows. To stop leaks, use weather stripping or sealant. Make sure there is unrestricted airflow by checking that all registers and vents are open.

Some common causes of short cycling include a furnace that is either too big or too hot, or outside influences that alter the voltage readings of the thermostat.

Troubleshooting Steps:

  • Thermostat Location: Avoid putting the thermostat in close proximity to a kitchen or other heat source, as well as any drafts that could come in through an outside door or window. Move if required.

  • Check the Air Filter and Flue: To prevent the furnace from overheating and turning off too soon, check the air filter and flue. If the filter is dirty, replace it. If the flue is clogged, clear it.

  • Look for Cracks in the Heat Exchanger: A cracked heat exchanger is another common cause of overheating and should be addressed by an expert.

Problems with the controls or settings could be to blame if your furnace appears to be blowing out too much air.

Troubleshooting Steps:

  • Fan Setting: Make sure the fan is turned on by examining the thermostat. The fan will run continually if set to "on," so make sure to change it to "auto" instead.

  • Check the Control Board: The fan's operation is controlled by the control board, thus any problems with it could cause the fan to not work as expected. Get in touch with an expert for replacement if you think there might be a problem with the control board.

water leakageWhen water starts to seep out of your furnace, it could be because of a blocked condensate drain, problems with the humidifier, or a broken heat exchanger.

Troubleshooting Steps:

  • Check the Condensate Drain: You should check the condensate drain and make sure that there are no obstacles in the line. Unclog if necessary.

  • Look for Leaks or Problems with the Humidifier: If your furnace has a humidifier built in, make sure you inspect it.

  • Heat Exchanger: Condensation from a broken heat exchanger could be the source of water. A specialist should look at this because it is quite serious.

There can be technical problems with your furnace if it makes strange noises at night like squeaking or slamming.

Troubleshooting Steps:

  • Belt Check: If the motor in your furnace is driven by a belt, you should check the belt for signs of wear and strain. Get a new one if it gets frayed or slips off.

  • Lubricate Bearings: For optimal performance, lubricate the bearings of your motor on a regular basis. To find out if this is relevant to your specific model, see the manual.

  • Component Adjustment: Panels or ducting that are out of place or loose might cause a rattling sound. Make sure the panels are fastened correctly and tighten any screws that may be loose.

Understanding every Lennox Furnace Error Code

Here’s a concise breakdown of common Lennox furnace diagnostic codes and their meanings:

Red and Green Simultaneous Slow Flash

There was no call for heat, thus this is a sign of proper operating. At this point, the thermostat has not signaled for heat, so the furnace is running properly but isn’t actively heating the house. Unless the homeowner wants heat and the furnace won’t respond to the thermostat, they don’t have to do anything.

Red and Green Simultaneous Fast Flash

The presence of this error code indicates that the heating cycle is functioning normally. When this happens, it’s because the thermostat has sent a signal to turn on the furnace. The furnace is behaving as expected, so there’s no need to do anything, similar to the slow flash.

Red and Green Alternating Slow Flash

When a homeowner notices this pattern, it means the heater is waiting for instructions from the thermostat or control system. This is a typical condition when the furnace is turned on but not producing any heat. Except in the event that the furnace does not react to the request for heat, no urgent action is required.

Red and Green Alternating Fast Flash

This means that the furnace is in lockdown mode because of a malfunction. The system takes this precaution to ensure the furnace is safe from harm or hazardous operating conditions. A clogged vent or a dirty air filter are two typical problems that homeowners should inspect. It is recommended to seek the assistance of a professional expert if the problem persists after performing the basic inspections.

Either or Both Lights On, No Flash

In most cases, a more significant problem, like the device losing power or a faulty control board, is indicated by this code. Before troubleshooting further, homeowners should inspect the electrical panel for blown fuses or circuit breakers. If the power is not out, then a professional technician will need to have a look at the control board and maybe even replace it.

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Red Slow Flash and Green Fast Flash

Pressure switches or inducer motor problems are common causes of this pattern. Any problems with the inducer motor’s operation or clogged vents should be immediately addressed by the homeowner. Because the problem can involve complicated component diagnostics and repairs, expert service is advised if unclogging the drains does not fix the problem.

Solid Red Slow Flash and Green On

The flashing of red and green at the same time is a common indicator of normal operation with a heat call. As long as it continues to provide heat, the furnace should not need any further attention.

Solid Red Slow Flash and Green Off

After a heating cycle, this code indicates that the system is entering cool-down mode. During this typical operating period, the furnace fan could keep turning to remove any remaining heat. Nothing needs to be done.

Solid Red Fast Flash and Green Slow Flash

There may be a problem with the gas valve or flame sensor if this happens. Maintenance on the gas valve, flame sensor, or both may be required. Gas components are complicated and sometimes dangerous, so it’s best to have a professional take a look.

Red On and Green Slow Flash & Red Off and Green Slow Flash

Depending on the context (whether it’s a call for heat or not), these codes indicate typical operation. They signify that the furnace is waiting for additional instructions or is currently heating up, respectively. Assuming the furnace is functioning normally, no further steps are needed.

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Additional Troubleshooting Tips for Lennox Furnaces

It is often possible to avoid this trouble by calling a professional to fix your Lennox furnace by troubleshooting it yourself. Here are some specific things to look for and things to keep in mind as you try to figure out what’s wrong with your furnace.

A furnace's control board is its central processing unit. Before troubleshooting, make sure the control board is free of obvious damage, such as burn marks or corrosion. For smaller issues, you might try resetting the board. The furnace can be reset by turning it off at the main power switch, waiting a few minutes, and then turning it back on. Occasionally, this will fix operational issues or error codes that are caused by temporary malfunctions.

When furnaces fail to ignite, it's usually because of a problem with the ignitor or flame sensor. These parts can become grimy or broken. If you want to be sure the ignitor can light the burner, check it thoroughly for cracks or too much accumulation. To keep the flame sensor working properly, clean it with a fine abrasive pad to eliminate carbon deposits.

Having troubles with the thermostat can be a sign of a more significant problem with the furnace. Check all the thermostats in the heating system are in the "heat" position and that the desired temperature is greater than the ambient temperature in the room. To fix a thermostat that won't turn on or shows no display, you need to change the batteries. Make sure the thermostat is set correctly and that all the cables are tightly attached.

You should check the air handler and blower motor if your furnace starts up but fails to blast air. You need to make sure the blower motor isn't clogged and can spin freely. The motor may not start if the capacitor isn't checked regularly because it can lose capacity over a few seconds' time. Use a multimeter to ensure the capacitor is in good working order if you're handy with electrical components.

Drying out the condensate is an important part of maintaining modern, high-efficiency Lennox furnaces. If the condensate drain becomes clogged, water will back up and your furnace could turn off. Locate and remove any blockages from the drain. Another thing to check for is a kinked or frozen drain line, both of which are prevalent in colder regions in winter.

Furnace efficiency might be drastically reduced due to clogged or leaking ductwork. Check the ductwork for obvious leaks or disconnections. Duct tape or mastic sealant can be used to seal leaks and greatly enhance performance. Also, make sure there is no wall or obstruction blocking any of your vents or registers so air may freely circulate throughout your home.

When to Call a Professional

Even though you can fix most furnace problems on your own with some basic troubleshooting, there are times when it’s best to hire a professional. There is a high potential for injury or more damage when working with furnaces, particularly those that use gas or have complicated electrical components. In order to prevent further damage or risk to your home, it is essential to identify when an issue goes beyond basic homeowner troubleshooting.

Get in touch with an expert right once if you think there may be a gas leak. Do not attempt repairs on your own if you detect the odor of gas near your furnace; instead, evacuate the area and call emergency services or alert your gas provider.

If you try fixing the problem multiple times and it keeps happening, it may be a sign of a more serious issue that has to be diagnosed and fixed by a professional. Exceptions to this rule include issues with the heat exchanger or ignition of the furnace, as well as persistent error codes that persist after standard resets.

In order to diagnose and fix certain parts of the furnace, such as the control board, blower motor, or wiring, one needs technical knowledge and access to specific tools. Improper management of these components can cause more issues or perhaps the system to fail entirely.

The warranty on your furnace can be nullified if you try to fix it yourself. If you want to keep your warranty valid, most manufacturers will only let repairs be done by a trained technician.

Call Comfort Union for all your furnace problems

Comfort Union provides efficient and affordable HVAC services from trained professionals whenever you need them. We have a staff of highly skilled technicians who are committed to fixing your furnace quickly while maintaining the finest standards in the business. Hiring reliable experts like Comfort Union ensures that your furnace is handled with care and contributes to its continued efficiency and longevity.

Call us for more details on repairs, installations, and maintenance of your HVAC system like your heat pump, air conditioner, and furnace.

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