Your HVAC’s thermostat is your communication center with your system. You need a thermostat to turn any HVAC device on or off or adjust the temperature in your home. But, when your thermostat’s screen goes blank, it is as if you don’t have a thermostat. So, when this happens, you must fix it as soon as possible to regain control of your HVAC system. But is it possible for you to troubleshoot and fix the issue yourself?
Troubleshooting a blank thermostat display screen is relatively easy, and the cause can, in many instances, be found and rectified by you without calling a technician or purchasing a new thermostat. The problem can be as simple as a loose connection or a screen with the level of brightness so low that it seems blank.
In this article, we’ll look at possible causes of the issue and provide general tips on fixing them. We’ll also discuss a few brand-specific solutions.
1. Verify that the display screen is really blank
The first thing you have to do when you detect that your thermostat’s display screen is blank is to verify whether it is actually blank or just seems blank. This may sound like a strange remark, but you can waste a lot of time if you troubleshoot a” blank screen” while there is no fault but it only seems as if there is no display on the screen.
Adjustable brightness levels
Some thermostats have display screens whose brightness levels can be adjusted, and just like a smartphone, the screen can seem blank if the brightness level is set very low and you are looking at the screen in bright light or from a distance.
If you’re unsure whether you can adjust the brightness of your thermostat’s screen, check your manual or consult the manufacturer’s website to find out whether it is a feature offered with your thermostat.
If it is adjustable, there is the possibility that your screen’s brightness level is set too low, and the screen just seems to be blank while it is actually working.
How the brightness level could have been changed
A power surge or an automatic thermostat reset after a power outage might have caused the screen brightness setting to change. So, if the brightness of your thermostat screen can be set, try to change the brightness level. If the screen stays blank, there is another fault somewhere, and you have to start troubleshooting.
2. Power supply issues
As your thermostat needs a power source to light up its display screen, one of the things to verify when your thermostat has a blank screen is whether it is receiving power.
Check the circuit breakers
Why should you check the breakers
If your HVAC or thermostat’s circuit breaker has tripped, no power is flowing to your HVAC system, including the thermostat. Your thermostat will then automatically start functioning on the internal battery’s power if it is equipped with a built-in battery, or on the changeable batteries if it is a model with batteries.
Whichever type of battery is used to power the thermostat, when there is no power coming from the circuit breaker, the batteries will, in time, drain completely. And as soon as the batteries are drained, the thermostat’s screen will go blank.
How to check and reset circuit breakers
So, if your thermostat is blank, check your home’s electrical panel for any tripped circuit breakers. You can gently test the switches – if it is securely in the “on” position (the switch in the “up” position), you can leave it, but if it is not fully engaged, put it off entirely by moving the switch downwards as far as it can go and then switch it on again. You’ll hear a click sound when it is in position.
If a circuit breaker has been off and you’ve put it on again, wait a few minutes to see whether it stays on or perhaps trips again. If it keeps on tripping, you have to determine why it is doing it. You’ll most probably have to call a qualified electrician to find and fix this electrical issue for you.
If the circuit breaker stays on, wait about 2 hours to give the internal battery time to charge, and then check your thermostat’s screen. You might find that you have fixed the problem.
Tip to remember
Remember, if the replaceable batteries have been drained while the main power supply has not been working, you have to replace them with new batteries after the main current flow has been restored. Thus, if the circuit breaker stays on, replace the batteries and check whether your thermostat’s screen lights up.
Check the batteries
Some thermostats are wired to your HVAC system, but the controls and screen display may be powered by replaceable batteries. You will experience a blank screen when the batteries are weak or dead.
How to find out whether replaceable batteries are drained
The easiest way to determine whether your problem is drained replaceable batteries is to replace the existing batteries with a new set of batteries. If the thermostat’s screen lights up when you’ve replaced the batteries, you’ve fixed the problem!
Just remember that you always have to insert only the batteries prescribed by the manufacturer. If you don’t have the manual anymore and can’t find the details on the manufacturer’s website, just replace them with the same type of batteries you are removing.
Tip to remember
After you’ve replaced the batteries and the thermostat is not blank anymore, it is good practice to check whether the system is receiving power from its primary source. An interruption in the power supply could be why the batteries have been drained.
3. Check the thermostat’s fuse as well as the HVAC system’s fuse
If a tripped circuit breaker or drained batteries are not the reason why your thermostat’s screen is blank, your thermostat or HVAC system may have a blown fuse.
Thermostat fuse
Put off the power to your HVAC system and thermostat and remove the thermostat from the wall. Open it and search for the fuse. It generally looks like a tiny, tube-like lightbulb with filaments in it.
If the filament is broken, the fuse is blown. A blown thermostat fuse results in a blank display screen. If the fuse is blown, replace it.
As with the replacement of batteries, ensure that you replace the fuse with the correct type of fuse as recommended in your owner’s manual. If you don’t have the manual anymore, you might find the details on the manufacturer’s website. Otherwise, just replace it with exactly the same type of fuse you are removing.
Put the power back on and check after a while whether you can now see the display on the thermostat’s screen. If so, you’ve found and fixed the problem!
HVAC fuse
A blown system fuse can also cause no power to go to the thermostat and its built-in battery. Thus, a blown system fuse might be the reason why your thermostat’s display has gone blank. Just as with a tripped circuit breaker, a blown fuse prohibits power from flowing to the thermostat’s battery, and in time, the battery is drained. And a drained battery causes the display screen to go blank.
To fix the problem, locate the system’s fuse and turn off the power to your HVAC system. Next, remove the fuse and look at the u-shaped wire visible through the fuse’s transparent “window.” The fuse is blown if the u-shaped wire is broken.
If the fuse is blown, replace it. After you’ve replaced the blown fuse, turn on the system again and if the display screen lights up in about 2 hours, the issue has been resolved.
4. Check whether the furnace door is closed
In most HVAC systems a low-voltage transformer on your furnace normally provides the most power to your thermostat. If the furnace is turned off the thermostat will not work properly. Most thermostats have an override which for safety reasons kicks in when the furnace door is open. This means the thermostat shuts itself off when the door opens. This results in a blank display screen on your thermostat.
To rectify the issue, ensure that the furnace door is closed. If the door is not open, ensure that the furnace switch is turned on. You can usually find this switch on the wall next to the furnace.
If your furnace doesn’t turn on, your furnace’s circuit breaker might be tripped. If you haven’t checked your circuit breakers already, do it now. Your thermostat screen should turn on as soon as the furnace is working again.
If the door has been closed and the circuit breaker is on but the display screen stays blank after about 2 hours, you have to troubleshoot further.
5. Check the purchase date of the thermostat
If your thermostat is ten years or older, there is the possibility that it has just stopped working, and you have to replace it. If you’ve done your troubleshooting and the display screen stays blank, it may be time to consider buying a new thermostat.
Some brand-specific solutions for a blank thermostat display screen
Trane thermostat – battery cycle
With a battery-powered Trane thermostat, you might be able to resolve the problem of a blank screen by executing a battery cycle on your unit. First, remove the 3 batteries from your Trane thermostat and leave them out for about 5 minutes to allow the power cycle to complete.
Then re-insert the batteries into the thermostat and see whether you can reread the display screen. In most instances, a battery cycle will solve the blank screen issue of your Trane thermostat.
Carrier thermostat – reboot
If your Carrier thermostat’s display screen is going blank, you might be able to resolve the problem by rebooting the thermostat.
To reboot your Carrier thermostat, gently pull it from the back plate. Check that all the wire connections are secured and put the thermostat back on the back plate. It should reboot automatically and provide a readable display on the screen again.
Ecobee – check the C wire
The Ecobee must always be connected to the power source to work correctly. Make sure that the R terminal and the power wire are connected securely. Check also the other connections by gently pulling the wires to confirm they are secure.
The Ecobee thermostat needs a C wire. Verify whether the C wire is connected. If not, connect it securely.
If you are using the Ecobee Power Extender Kit with your Ecobee3 or Ecobee4 model, check that the wiring is attached correctly:
- R wire must be connected to the R terminal on the thermostat,
- the G wire to the thermostat’s C terminal,
- the W wire to the W1 terminal, and finally
- the Y wire to the PEK terminal.
When everything is connected correctly and you put on the power again, the thermostat’s screen should light up.
Nest – UBS-charging
If you have a Nest thermostat like the E and Nest Learning thermostats with built-in batteries, the battery can be drained and cause the display screen to go blank. But you can charge the Nest thermostat with a UBS cable as a temporary solution.
To charge your Nest thermostat with a USB cable, you have to remove the Nest thermostat’s display from the base. Then insert a USB cable into the USB port on the back of the thermostat, put the other end in a charger, and plug it into a power outlet. The Nest thermostat screen should now turn on. But remember, you’ll still have to find the actual problem why the battery has been drained to fix the problem permanently.
Conclusion
It is very frustrating if you want to set or check something on your thermostat and the display screen is blank. Fortunately, in most instances, the problem can be found relatively quick and easy and you can rectify most of the issues yourself. So, don’t replace your thermostat before you’ve done proper troubleshooting.
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