It’s an “Oh no!” moment when you approach your home’s thermostat and see its screen is blank. Is it serious? Does it mean your furnace, heat pump, or air conditioning is broken? Not necessarily. In fact, most of the time, it’s something minor and can be easily fixed.
Here are some of the most frequent reasons our Chris Mechanical technicians see a thermostat blank screen:
If your thermostat wall does not have a c-wire, or common wire, your thermostat most likely is not hooked up to your HVAC system for its power and needs batteries. When your screen is blank, it could indicate you need to replace the batteries. It that is the case, you typically need AA alkaline or 3-volt lithium batteries, but see what type is currently powering the thermostat and simply replace them. Most thermostats display a low-battery symbol when the juice is running low.
On the other hand, if your thermostat is hardwired to your HVAC system for power, it could be a temporary blank screen if the thermostat is in the middle of recharging. Wait a short time and see if the display returns. If it does not, read on.
Loose wiring or wiring problems.
Sometimes the wires hooked up to your thermostat are responsible for its lack of power. If they were not firmly attached originally or the thermostat is in a high-traffic room, the vibrations from people walking by can sometimes affect the wires. Our technicians have also seen wires chewed by rodents in attics affect the wiring. Since wiring deals directly with electricity, we recommend you calling us to diagnose and repair the issue for you. When it comes to electricity, it’s better to be safe than sorry.
Tripped circuit breaker or blown fuse.
A quick fix to restore your thermostat’s power is a tripped circuit breaker or blown fuse, depending what you have in your home. Sometimes a surge can cause this issue. If you check your electrical box and a circuit breaker is tripped, just flip it back. If you have fuses, replace the fuse. Once this is done, check your thermostat. If you have power again, you are set; but if the breaker trips again or the replacement fuse blows, you have a more involved HVAC problem. You need to get a professional involved.
Tripped safety switch.
HVAC systems have built-in safety switches in the case of an unsafe situation. In the event a safety switch on one of your units is tripped, the transformer supplying voltage to your unit (and possibly your thermostat) will stop power. If this is a furnace, you need to call in a professional for a diagnosis and repair. If it’s your heat pump or air conditioner, check its condensate pan to see if it’s full. As a safety precaution, this will trip the safety switch. Empty the pan and see if power is restored to your unit and thermostat. If not, you need a professional.
Open furnace door.
Every once in a while, our technicians come across this issue. Some thermostats are more sensitive to this issue than others, but it is something worth checking. If your furnace door is not closed tightly, your thermostat will turn off. Simply closing the door securely should restore power if this is the cause.
Though thermostats can last 10 to 20 years, they do wear out. Sometimes it is just time to replace it. If your thermostat is older, unfortunately this may be the problem. If it is, be sure to have a professional install the new one, since the newer ones can be complicated, and you want to be sure you will not have issues with it in the future.
At Chris Mechanical here in West Chicago, IL, we frequently field phone calls regarding thermostat issues. If your thermostat has a blank display, try these ideas to see if you can restore its power. But if they are not solving your problem, or if you are hesitant about attempting these on your own, please call us at 630-206-5093. We would be happy to help.