Why Does My Thermostat Go Blank then Come Back On? We Have Solutions

Has your thermostat screen ever suddenly gone blank, only to mysteriously turn back on after a while? This intermittent issue can be alarming and frustrating for homeowners relying on their thermostats to regulate indoor temperatures.

A thermostat screen going blank temporarily is usually indicative of a power supply disruption. When the thermostat loses power, even for a second, its screen will turn off. Once power returns, the screen illuminates again.

Possible Causes of a Thermostat Screen Going Blank

There are a number of reasons why your thermostat might be losing power and causing the screen to go dark intermittently. Here are some of the most common culprits:

Low or Dead Batteries

Thermostats that operate on batteries are prone to power issues as the batteries start to drain. Alkaline batteries provide 1.5V of power when fully charged. As they discharge with use over time, the voltage drops. Once it falls below the level the thermostat needs to operate, the screen will go blank. Dead batteries equal zero power.

Check the battery levels if your thermostat requires them. Ideally the batteries should be replaced proactively before they die completely. Choose name-brand alkaline batteries of the correct size specified by the thermostat manufacturer. Improper or old batteries are a common reason for thermostat screens losing power temporarily.

Dim Screen and Display Settings

Many programmable and smart thermostats allow users to adjust the display and brightness levels. While this helps for nighttime viewing, setting the brightness too low can make the screen appear blank occasionally.

If your thermostat screen is going dark intermittently, tap it or press buttons to wake it up. Check the display settings and turn up the brightness as needed so the screen remains clearly visible. Be aware that very low brightness levels can cause the illusion of a blank screen.

Power Outages

Losing power to parts of your home can cause a thermostat screen to go blank. Issues like tripped circuit breakers, malfunctioning electrical components, and blown fuses interrupt the power supply temporarily. When this happens, the thermostat loses power too.

Check breakers and fuses if your thermostat screen goes blank without any obvious reason. Reset tripped breakers and replace blown fuses as needed to restore continuous power. If these do not resolve the issue, contact an electrician to inspect your electrical system.

HVAC System Problems

Thermostats are integrated with your home's HVAC system. Issues on the heating, ventilation and air conditioning side can sometimes disrupt power to the thermostat as well. For example, a problem with the furnace or AC unit may cause a safety switch to trip and cut power as a precaution.

Have your HVAC system inspected by a professional if you suspect issues on that end are causing the thermostat power loss. They can identify and resolve the problem, which should prevent the screen from going blank randomly.

Loose Wire Connections

Thermostats have wire connections that send power and data back and forth between the thermostat unit and the HVAC system. If these wires become loose, it can interrupt the power supply and cause the screen to turn off.

If your thermostat relies on wiring, inspect the wire terminals on the thermostat and at the HVAC system to ensure all connections are tight and secure. Tightening loose wires may be all that's needed to keep consistent power flowing.

Faulty Thermostat Wiring

While loose wires cause temporary power loss, completely damaged or improperly installed thermostat wiring can cause ongoing intermittent issues. Frayed, cracked or otherwise faulty wires cannot transmit power reliably from the HVAC system to the thermostat.

Consult a technician to test your home's thermostat wires if simple wire tightening does not resolve the problem. They may advise replacing old thermostat wires to prevent wiring problems from making your screen go blank.

Open Furnace Door

Some thermostat models are designed to power off when the furnace door opens. This is an intentional safety feature to avoid operating the furnace with the door ajar.

If your thermostat goes blank randomly, check that the furnace door is properly shut. Closing it securely can restore power to the thermostat. Just be sure not to open the furnace door until completely cooled down.

Other Less Common Causes

Malfunctioning Humidifier

In some cases, a malfunctioning humidifier attached to your HVAC system can cause the intermittent thermostat blanking. Humidifiers increase moisture in the air, which can give false readings on the thermostat and trick it into thinking the desired temperature has been reached when it actually hasn't. Have your humidifier serviced if you suspect it is not working properly.

Dirty Air Filter

As air filters accumulate dust and debris over time, airflow through your HVAC system becomes restricted. This can cause the evaporator coil to freeze. The frozen coil blocks airflow even further and lowers the temperature on the thermostat sensors. These false low readings can disrupt power to the screen.

Check your furnace air filter monthly and replace it as soon as it appears dirty. Letting the filter get too clogged can lead to frozen evaporator coils and thermostat blanking episodes.

Faulty HVAC Wiring

Faults in the wiring between your thermostat and the HVAC system components can also cause power loss. These wires send electrical signals to control your heating and cooling equipment. Damaged wires prevent proper operation and cut power unpredictably.

A technician can identify if HVAC wiring issues exist and make repairs to establish consistent power flow to the thermostat. This should stop the screen from cutting out intermittently.

Thermostat Defects

In rare cases, a bad thermostat unit itself can be the culprit. Defective components lead to problems regulating and delivering power. So the thermostat ends up turning off randomly, even when external conditions are fine.

If your thermostat is still under warranty, contact the manufacturer for a replacement. Otherwise, replacing an older thermostat that is no longer functioning properly can provide a permanent fix.

Preventing Future Thermostat Screen Blanking

While occasional thermostat blackouts are normal, you can take steps to reduce occurrences.

Taking proactive measures allows you to catch and resolve small problems before they can cause bigger issues like intermittent power loss to your thermostat screen.

Calling in a Professional

DIY troubleshooting can diagnose and fix many common issues causing a thermostat screen to go blank temporarily. But if you've checked the basics thoroughly and the problem persists, it may be time to call in an HVAC technician for assistance.

A professional can test all system components to pinpoint elusive issues. They can check for wiring problems, equipment faults, and other problems that DIYers can miss. Technicians have specialized tools and testing capabilities exceeding what homeowners typically possess.

It's also wise to have a qualified HVAC technician do annual maintenance on your entire system. They may catch and correct small problems that could lead to thermostat blanking when left unaddressed. Taking preventive measures can restore peace of mind.

A thermostat screen that goes blank momentarily can certainly be annoying. But in most cases, it is a relatively minor issue caused by temporary power interruption. Once the underlying problem is identified and corrected, normal operation will resume.

Battery issues, wiring faults, electrical problems, and HVAC malfunctions are the most prevalent causes. With diligent troubleshooting and proper maintenance, you can determine the cause and prevent future occurrences. Just be glad that the blank screen is temporary rather than permanent!