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Is your thermostat’s screen blank even after several efforts of turning it on? The problem might be that there’s no power going to your thermostat. If this is the case, we’ve listed the most common reasons why your thermostat is powered off along with how to fix the situation.

At SmartHomePerfected we always advise readers not to undertake any work they are not competent in performing and if in any doubt, it is best to seek the assistance of a professional.

1. Check the Thermostat

The first and most obvious thing to do is check if the thermostat display powers up. Press a few buttons to see if you get a response. If the screen doesn’t come on, you should continue our diagnostic steps below. Alternatively, if you have just installed the thermostat, there may be problems with your installation.

2. Check Power Supply

The most common cause is a problem with the power supply.  Check to see if the circuit breaker hasn’t tripped or the fuses haven’t blown.  

You can easily find out if the circuit breaker has tripped by checking the safety switches in your HVAC system. Simply turn on the switch to restore the power supply. However, if a fuse is blown, there’s no way around it. Thus, you will have to replace the blown fuses with new ones. 


In many cases, a tripped circuit breaker or a blown fuse is caused by a power surge.  Alternatively, power problems may be connected to the main supply. For example, if your thermostat needs 240V input and is connected to a 120V power supply, it will not work. 

Alternatively, the power problem may be within the HVAC system. To protect the user, HVAC systems are built with safety switches that work like circuit breakers. Thus, if this happens, simply turn on the switch. If the problem persists even after turning the switch on, simply call an HVAC expert to assist.

3. Check the batteries

If the power supply isn’t a problem and the screen on your thermostat still won’t come on, chances are that the batteries have died (although some thermostats will have a low battery indicator before the screen completely dies off). 

Alternatively, if your thermostat is hardwired, it may be a temporary problem – maybe your thermostat is recharging. With thermostats that depend on batteries, replacement is almost similar. For example, Honeywell thermostats require that you remove the faceplate using a handle at the bottom. 

Once the plate is removed, you will have access to the thermostat’s interior, where the batteries are.  You can then replace them.  If you have a touch screen thermostat, press the button attached to the bottom to open the faceplate. When done, attach the faceplate to the notches at the bottom of the thermostat to close it.

4. Check the wiring

Your next step is to check the wiring. The common issues with wiring can be wires that have disconnected, are loosely connected, or have burnt. Thus, you may have to reconnect them or replace them if they are damaged.

To make sure the wiring is connected correctly, follow the steps below:

  • Turn off the power
  • Open the thermostat’s faceplate and physically examine the wires and terminals to ensure they are tightly connected. You especially want to pay attention to the red wire with the R/Rc/Rh terminal. If there is any loose connection, fix it.
  • Next, if your thermostat requires a C-wire, make sure the connection is intact and proper.
  • Lastly, check other HVAC components to ensure they all function. If the components don’t conduct, the circuit won’t be complete, and your thermostat will not receive any power.
  • Turn back on the power

If your thermostat’s wiring to the indoor unit control board is done incorrectly, this will most certainly cause power problems. Either the thermostat's poor functioning will result in higher costs, or the unit won’t start at all.

Wire types

To the untrained eye, it may be difficult to confirm whether or not the connection is right. So, you have two methods to guide yourself. You can refer to the color-coding of the wires or a drawing of the connection on your thermostat’s user manual.

However, If you think the problem is with the wiring and can't really diagnose the main issue, it is good to call an HVAC expert to assist. You certainly want to exercise more caution when it comes to electricity!

5. Check if the thermostat is clean

A dirty thermostat may disrupt the power supply too. Therefore, you have to clean the interior of your thermostat to rid it of dust and debris from time to time.

Cleaning your thermostat will not only sort out the power problem but also help improve its efficiency. While you can find different thermostat models and designs in the market, cleaning them follows pretty much the same method.

The only difference is usually between faceplate opening mechanisms – some snap off while others slide.

To clean a thermostat:

  • Turn off the power
  • Remove the cover or faceplate.
  • Using a soft-bristled brush or compressed air blowing tool, clean between its switches and other components.
  • Between the smaller crevices and contact points, use a thin piece of cloth or cotton buds to clean out dust and debris. *Make sure you don’t touch the interior with your fingers to avoid damages.
  • After cleaning the interior, immediately reattach the cover or faceplate and turn back on the power.

While cleaning thermostats is essential, there are also some limitations. For example, if you have a smart thermostat in your home, avoid cleaning its interior! All you have to do is clean the exterior surfaces and wire terminals in the back.

Perhaps it’s time to replace the thermostat?

In some cases, the common problems above may not be the factors after all. Or, if you find yourself frequently addressing these issues, it may be that your device needs replacement. If you have been with the same thermostat for many years, it is definitely time for a replacement.

The Verdict

If you know how to diagnose and solve the common problems addressed above, rest assured, you will be able to fix your thermostat’s power issue. But, if you keep on experiencing these issues with increased intervals and if your thermostat is old, the chances are that your device needs replacement.


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