Your Pro1 T705 thermostat has stopped working and you want to fix the issue yourself but now you wonder how you should do the troubleshooting. Is it even possible to do it yourself? 

The most possible reason why a Pro1 thermostat T705 is not working is an incorrect setting of the HVAC system switch or the fan switch. If the display is blank, the cause is most probably dead batteries. These problems can easily be solved by replacing the batteries and resetting the thermostat

In this article, we’ll discuss the most common causes that might be the reason that your thermostat has stopped working, and offer tips and guidelines on how to determine the exact cause. Depending on the cause, you might be able to fix the issue yourself. 

Pro1 T705 Programmable 1H/1C Digital Thermostat

How do I know if my Pro 1 T705 thermostat is probably broken?

When your thermostat is not working, it is not necessarily irreparable damaged.  Generally, there are three main signs telling you that your thermostat is most probably broken.  If you experience any of these signs, troubleshoot it and if you can’t get it fixed you have to call a technician for further tests and will probably have to replace your thermostat.  

  • The thermostat’s display is dark or if it is readable, it is non-responsive. 
  • When you turn on the heat or the AC they don’t start working. 
  • The heat or the AC will come on for long periods although the thermostat is off, or stays on nonstop. Sometimes they cut out before the temperature setting is reached.

Can Incorrect settings let my thermostat malfunction?

Incorrect settings might cause your thermostat to malfunction and even stop it from working. If your Pro1 thermostat isn’t working, your first step should be to check whether all settings are correct. 

The most important switches that have to be correctly set, are the HVAC system switch and the fan switch.

Settings for the HVAC system switch

You use the system switch to select the operation mode of your HVAC system. There are three mode options: heat, cool, and off. 

By selecting “heat” you turn on the heat mode. Selecting “cool” mode will turn on the air conditioning mode. If you select “off” you turn off both heating and cooling. For your thermostat to work effectively the switch mode has to be set either on “heat” or “cool.”

Settings for the fan switch

The fan switch has to be set to either “on” or  “auto.” Ensure that the switch is set to one of these options. Selecting “on” lets the fan run continuously while “auto” will activate the fan when the cooling or heating system is on. If no option has been selected your thermostat might stop working. 

Can issues be resolved by resetting my Pro 1 thermostat?

It doesn’t matter what the issue is, there is always the possibility that resetting the thermostat might solve the problem. Thus, the next step after checking the settings is to reset the thermostat. And if you are successful with this step, you will save yourself lots of time for looking for problems that don’t exist!

Just like your cable modem, your Pro digital thermostat sometimes kicks back into shape after being reset. It is actually recommended by technicians to reset your digital thermostat every once in a while. Whenever the temperature in your house is not regulated as good as before, it is also a good idea to reset your thermostat. This often prevents larger future possible problems.  

You can reset your Pro 1 thermostat by power cycling. In other words, put it off completely, wait 10 to 15 seconds and put it on again.  The best way to power cycle the thermostat is by removing the batteries and putting them back again.  To remove the batteries you will have to remove the thermostat from the subbase. 

Two common thermostat problems and how to troubleshoot the issues

Two symptoms of a thermostat that is not working are a dark display, or if the display is readable, you can’t activate HVAC functions via the thermostat. If you can pinpoint and fix the problem it may save you money because you won’t have to get an HVAC technician to make the diagnosis. 

The thermostat’s display is dark

If your thermostat’s display is dark, it is normally because of a lack of power. Take out the batteries, ensure that the holder is dry and dust-free, and replace the batteries with new ones.  

If the display stays dark, check whether the circuit breaker has tripped. (In older houses without circuit breakers, check for a blown fuse.) The circuit breakers or fuses are on the electrical panel of your home.

Put the circuit breaker on again or replace the blown fuse. Just remember that if the breaker has tripped, you have to completely click it off and then on again. 

If the thermostat’s display is still dark, shut off the power to the breaker, shut down the breaker and remove the thermostat’s cover.  Use a soft brush or canned air to clean away any dust and grime that might affect connectivity. Put everything back again and if this has also not been successful, check all the wiring and terminal screws. 

If the display is still dark, you have to consult a technician to either repair the thermostat or replace it.

The thermostat setting and room temperature don’t match

There may be no fault with the thermostat’s display but the thermostat’s setting and the room temperature don’t match, and thus, the thermostat is not working

This can be caused by a dirty thermostat. To clean the thermostat, shut off the power to the circuit breaker, shut down the breaker and remove the thermostat’s cover.  If there are dust and grime in the thermostat, clean it away with a soft brush or canned air. 

While the thermostat is open, check all the wires and connections. Clean and fasten again if needed. 

If the temperatures still don’t match after a while, consider the possibility that the thermostat could have had a bump and has been damaged.  You can also consider moving the thermostat to another location where it is not exposed to direct sunlight or drafts.   

If the temperature difference persists you’ll have to call a technician. 


When your Pro 1 thermostat t705 is not working, it is not necessarily broken. It is often a result of a power loss or incorrect settings and you’ll be able to fix it. 

If follow the steps we’ve discussed in this article you might be able to pinpoint the problem and fix it. Unfortunately, if the thermostat is still not working after you’ve tried all the solutions offered, you’ll have to call a technician to determine whether there are other problems.  


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