Lennox Thermostat Blank Screen [Quick Fix]

So your Lennox thermostat screen has suddenly gone blank, and you’re not sure what to do? Keep reading to see why this happens and how you can fix this issue yourself.

Your Lennox thermostat screen may go blank because of the following reasons:

Your battery is completely dead
The wiring in your Lennox thermostat is faulty.
Your thermostat’s circuit breaker tripped.
The safety switch in the HVAC system is turned off.
Your Lennox thermostat has reached the end of its lifespan.
You left your furnace door open.

Keep reading to see how to get your Lennox thermostat screen back on.

Table of Contents

How to Fix Lennox Thermostat Blank Screen Problems

1. Replace Your Lennox Thermostat Batteries

Your Lennox thermostat screen will go blank if the batteries are dead.

As you probably know, the thermostat requires functional batteries to run effectively. So, when the batteries are low/dead, it might affect some features. And one of such features is the screen, which may become blank when the batteries stop working.

If your Lennox thermostat screen suddenly goes blank, the batteries might be low. So, you may need to replace the batteries to fix the problem.

Follow the steps below to change your Lennox thermostat batteries:

Unmount your Lennox thermostat from the wall by carefully pulling it out of its wall plate.
Next, turn it over to reveal the battery compartment.
Open the battery compartment and take out the old batteries.
Insert the new batteries into your thermostat. Your Lennox thermostat needs 2 AAA Alkaline batteries.
Close the battery compartment and remount your thermostat to the wall.

If this doesn’t help (the screen is still blank), continue to the next step.

2. Turn on Your Thermostat’s Circuit Breaker

If you experience a power surge/outage in your home, your thermostat’s circuit breaker may flip off. As a result, the thermostat screen might become blank.

So, if all the details on your Lennox thermostat screen suddenly disappear, you might need to check whether the circuit breaker is turned on. If not, flip it back on.

Once you switch on the circuit breaker, the thermostat may regain power. This should turn on the screen.

However, your thermostat’s circuit breaker may flip off immediately after you turn it on. If this happens, your HVAC might be faulty. Get an HVAC expert to fix your HVAC system if your thermostat’s circuit breaker keeps turning off.

3. Turn on Your HVAC’s Safety Switch

Is your Lennox thermostat screen still blank after turning on the circuit breaker? Then your safety switch might have gone off.

While installing your Lennox thermostat, you link the wires on your HVAC (Heating, Ventilation, Air Conditioning) system to the device. The thermostat, thus, becomes connected to your heating and cooling systems. So, when the safety switch on your furnace or AC goes off, it might affect the functioning of your thermostat.

For instance, your thermostat screen may go blank if the safety switch on your furnace turns off.

To resolve this issue, turn your safety switch back on. But the safety switch is located within the drain pipes of your heating and cooling system, so you can’t turn it on by pressing it. How do you put on your safety switch?

One quick way to turn on the safety switches on your AC and heat pump is to empty their drain pans. When the HVAC system’s safety switch goes off, it is usually because the condensate pan in your heating or cooling system is full.

The purpose of the safety switch is to prevent water damage to the HVAC. The switch achieves the process until the drain pans become full, after which it stops working and goes off.

If you want to turn the safety switch back on, you have to remove the water in the drain pans of your AC/heat pump.

Follow these steps to remove water from your drain pan:

Turn off your Air Conditioner or heat pump.
Unscrew the PVC cap from the drain pipe.
Use a dry vacuum to take out the water from the drain pipe. Now, you have removed the water. But you’ll still need to clean the dirt in the pan.
Clean the inner parts of the pipe with a wire brush. You can also use bleach to remove the dirt.
Replace the PVC cap once you’ve unclogged the dirt.
Now, switch on your HVAC system.

4. Close Your Furnace Door

Your Lennox thermostat may display a blank screen if your furnace door isn’t properly closed.

An open furnace door may prevent your furnace from turning on. By extension, your thermostat screen may go off.

If your Lennox thermostat suddenly displays an empty screen, check and ensure your furnace door is closed. Remember to keep the furnace door tightly closed to prevent the furnace from turning off.

Once you close your furnace door, the furnace should start working; and your Lennox thermostat screen should turn on.

5. Fix Your Lennox Thermostat Wiring

Loosened or pinched wires may also be the reason your Lennox thermostat screen is blank.

If your Lennox thermostat screen is still blank after trying the fixes above, the problem may come from the wiring.

Open the thermostat and check the terminals and ensure all wires are inserted into the right terminals. Also, check and fix pinched wires.

However, note that wiring issues are best left for professionals to handle. Handling electrical wires without expert knowledge can be dangerous, so it is best to call an expert to check and repair the faulty wires on your thermostat.

6. Get a New Thermostat

If you’ve been using your Lennox thermostat for over 10 years, the screen may go blank from time to time. This could be a sign that your thermostat needs a replacement.

Your old thermostat’s display may never reappear on the screen even if you repair it. So, it’s best to buy a new Lennox thermostat to provide a lasting solution to this issue.

Closing Thoughts

As you can see, you can troubleshoot blank screen issues on your Lennox thermostat without making that expensive service call.

For the most part, replacing the batteries and resetting the thermostat (flipping the circuit breaker off and on) should fix the blank screen problem on your Lennox thermostat. However, if none of the fixes work for you, contact Lennox Customer Support or replace the thermostat.

You may also like to see how to fix blank screen issues with a Trane thermostat, Bryant thermostat, and Braeburn thermostat.