What Can Cause a Thermostat to Go Blank?

South End Plumbing, Heating, & Air Expert Tips

What Can Cause a Thermostat to Go Blank

Is your thermostat’s screen blank? A blank thermostat display can be a major issue, and cause major panic, or it could be very simple. But, specifically during winter months or the hot summer, you need your thermostat to operate your heating and cooling system. Don’t worry, there could be a quick and simple solution. First, let’s try to find out why a thermostat can go blank.

The Thermostat is Off

Let’s start with the basics. Has the thermostat been turned off? Before any other fixes, calls or stressing, see if the thermostat is on or off. It could’ve been turned off, even just by accident.

Check the Batteries

Next, and another simple step which is a common answer, check and probably change the batteries in the thermostat. Even if there is still some power in the batteries, dying batteries can cause power blips and outages in a thermostat. So if your thermostat goes blank and then comes back on, try new batteries and see if that solves it. Most thermostats will display an indication or a beep for low battery. Depending on the kind of thermostat you have and the batteries it uses, you might need to replace them every couple of years. Other thermostats could need new batteries much more often.

Tripped Switch

If your thermostat screen goes blank after the unit’s been on for a few minutes, it could be due to a high-limit switch tripping. Most heating systems have a high-limit switch that prevents the system from overheating. Overheating typically takes place because of inadequate air movement or parts that are failing or broken.

Check the Display Settings

If your thermostat lets you to change display settings such as the brightness level, be sure to check that the brightness or display isn’t turned down. Some thermostats will also auto-dim the screen at specific times of the day or when there is way too much light around it.

Furnace Door is Open

Some thermostats, especially Honeywell thermostats, will go blank if the furnace door isn’t completely shut. Check that your heating system door is not open and shut it securely and see if that fixes the trouble.

Breaker Issue

Programmable thermostats, including wireless devices, are typically linked to the house’s electric system. If the breaker trips then it could shut off power to your thermostat and if there’s no battery backup, the screen will be off.

If there was recently a power surge in your house or you have been running several appliances at the same time, this may be your problem. Every homeowner should know where their electric box is and how to turn the whole system off and on in case of an emergency or simple accident. Reset the circuit breaker and see if the display switches on. If the display is still blank, then it could be time to replace the thermostat.

Float Switch

A lot of new furnaces and air conditioning systems have safety sensing units, called a float switch, wired to the thermostat. If the sensing unit discovers high moisture, it will turn the system off. In numerous circumstances, these switches misread their environments and just need to be reset. This switch going off could be a sign you have a clogged air conditioner drain line.

Wiring Issues

A thermostat has many electric connections that serve different functions from the screen display to having the thermostat connect with the HVAC system. If you just recently had a thermostat set up or installed it on your own, this may be your issue. Unless you have electrical expertise and know what you’re doing, we don’t suggest trying to repair loosened connections or electrical wiring problems on your own.

Dirty Wiring

You might not check the thermostat, around it or behind it until there’s a problem. You might not think of this, but dust can collect in the wiring. If other checks or steps haven’t fixed the display issue, remove the cover to your thermostat and examine the circuitry. It could just by dirty and gunky. If there is a visible amount of dirt, use a soft brush or compressed air to clean the wiring.

Dirty Air Filter

Have not changed the air filter in a while? It could be a reason why your thermostat is malfunctioning. The filter in your HVAC system gathers, by design, dust, dirt and other particles. If it’s dirty and clogged, it impedes airflow and can trigger a system shutdown. Look at your air filter. If it’s old or dirty, replace it. Make sure to replace filters often – it’s usually recommended for every 1-3 months.

Blown Fuse

Some thermostats have a fuse inside for added security from power surges. If the fuse is blown, your thermostat will not work and you’ll need to replace the fuse.

You’ll need a multimeter for finding this one. Walk outside to your AC condenser unit. Near it, on a wall of your home, you’ll find the fuse box. Check each fuse (one at a time) with a multimeter. This will test voltage left. If one fuse has no voltage, you can purchase a new one online or at any hardware store.

Mismatched Parts

Have you recently replaced any parts or components, interior or exterior, in the HVAC system? All of the parts in an HVAC should interact and be compatible. Replacing a single component occasionally can foul up the entire system if the part isn’t right.

Replacing the Thermostat

You’ve reached the end of, this list of possible ideas anyway. If there’s no other explanation, the blank thermostat might need to go. The ordinary life of a thermostat is about 10 years, but this number varies on lots of circumstances. If your thermostat is more than a decade old, it may be time to upgrade anyway.


At South End Heating and Air we are Charlotte’s affordable AC experts. Call us anytime for a free consult and free estimate. We’ll evaluate your system and help make recommendations for optimum value. After all, we want to keep you cool all summer long and warm in the winter. Just schedule a visit with one of our technicians to talk about how we can help. Would you like to learn more options our techs can help you with? Give us a call 704-684-5339.

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