Pro 1 Thermostat T705 Not Working? (Possible Causes & Fixes)

Nick Durante
by Nick Durante

The Pro 1 t705 is an effective and versatile thermostat that is ideal for many homeowners. It can run solely on batteries, a hardwire, or a combination of both for consistent performance. With that said, what are you supposed to do when your Pro 1 t705 thermostat is not working?

Pull your Pro 1 t705 thermostat away from the base and remove its batteries to reset it if it’s not working. Remove the thermostat face and clean the wiring with compressed air or replace the air filter to make it work. Reset the circuit breaker, replace your batteries, and look out for faulty wiring if the t705 doesn’t work properly.

You can generally fix your Pro 1 t705 thermostat in a matter of a few minutes. Follow along as we explore why your Pro 1 t705 is not working and see what you can do to troubleshoot it.

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Why Is My Pro 1 Thermostat Not Working?

A pro 1 thermostat can stop working due to faulty wiring, low batteries, dirty air filters, and more. It can be difficult to identify the cause of your Pro 1 t705 thermostat problems if you don’t know what to look for. Let’s take a look at the reasons why your Pro 1 t705 thermostat is not working.


Just like any other appliance, a Pro 1 t705 thermostat cannot work properly when it’s dirty. Depending on its location, a thermostat can generally take on plenty of dust and debris. This dust and debris can accumulate around the wires and other internal components necessary to operate well.

Too much dust can make any thermostat, including the Pro 1 t705 underperform or not work at all. It is worth the time to remove the cover from your thermostat to check for excess dust and debris if your Pro 1 t705 isn’t working properly.

Faulty Wiring

Pro 1 t705 thermostats take batteries, but you can also hardwire them. However, you won’t get very far if you don’t wire your Pro 1 t705 thermostat properly. It is easy to make simple mistakes when you hardwire a thermostat, and that is why it is helpful to hire a professional.

A Pro1 t705 uses a C-wire, or common wire, either on its own or along with batteries. Many homeowners use batteries and a C-wire as a backup and to help power the t705 thermostat. You are more likely to run into problems if your Pro1 t705 thermostat is solely battery-powered and doesn’t have batteries.

Tripped Breaker

Was your Pro 1 t705 thermostat working fine and suddenly isn’t working at all? That often indicated that the circuit breaker was tripped. An overwhelming electrical current can cause a circuit breaker to trip as a safety measure.

You can usually tell that the circuit breaker is at the root of the problem if you had a recent power outage or surge. Running too many electrical appliances on the same circuit is another surefire way to cause your breaker to trip.

Dirty Filter

Pro 1 t705 thermostats won’t work effectively if you have a dirty air filter. Luckily, the display on a t705 presents a “FILT” message that indicates the filter is dirty. If the filter is too dirty, however, your thermostat and HVAC system won’t work to their fullest potential.

Dirty filters force your HVAC system to work harder, and it may shut on and off right away. Dust, dirt, and debris greatly reduce the airflow in your air conditioner, and it may not work at all. Pro 1 t705 thermostats may not respond to your settings when the filter is too dirty, and you’ll have less control over your AC.

Low Batteries

Your Pro1 t705 can display a low battery warning, and it is wise to pay attention to it. If you let it go long enough, the display screen will solely display the battery icon. You won’t be able to control your Pro 1 t705 thermostat, and therefore, you can’t control your HVAC system with low or dead batteries.

The same can be said if you put the wrong kind of batteries in your Pro 1 t705 thermostat. Your Pro 1 thermostat will only work if you use two AA batteries. Batteries can last for up to 12 months in a thermostat, but it is wise to replace them when the low battery icon appears.


Troubleshooting your Pro 1 t705 isn’t difficult, and each solution is mostly simple. Some solutions, such as replacing batteries or resetting the thermostat only take moments. Advanced troubleshooting can include rewiring your Pro 1 t705 thermostat.

Let’s take a look at the most common solutions to a Pro1 t705 thermostat that isn’t working.

1. Compressed Air

Compressed air is the most effective way to safely clean your Pro 1 t705 thermostat. Remove the face to your thermostat and inspect the inside for dust and debris. Carefully use compressed air to clean the dust off of the wires without damaging them.

This is a great solution if your t705 is hardwired, but it works if you have batteries as well. You can always remove the batteries and hit the compartment with compressed air if it is dirty.

2. Adjust Wiring

If your Pro 1 t705 has faulty wiring, you need to adjust it. However, it is a great idea to hire an HVAC professional or electrician if you have limited experience. Hardwired thermostats simply won’t work without proper wiring, and they work at a limited capacity if they have backup batteries if the wiring is wrong.

3. Reset

Resetting your Pro 1 t705 thermostat can often fix it when it’s not working properly. You can reset your Pro 1 thermostat by power cycling it, and it only takes a moment. Gently pull the thermostat face away from its base and remove the batteries.

Leave the batteries out of the thermostat for 10 seconds and put them back in the battery compartment. Reconnect the thermostat face to the subbase to reset the Pro 1 t705. This reset works for solely battery-powered units.

4. Reset Breaker

Reset your circuit breaker if it recently tripped. Simply flip the switch from “off” to “on” and see if your thermostat will start working. The t705 may not start working again right away if there is a bigger problem, such as too strong of a current on that circuit.

In that case, you can try to limit how many electrical appliances you plug in on that circuit. You will likely have to reset your circuit breaker after power outages so that your Pro 1 thermostat works properly.

5. Replace Filter

Replace your air filter if it is dirty and prevents your Pro1 t705 thermostat from working. Turn off your AC and put your filter in so that the arrow directly faces the unit. It is smart to replace air filters every 2 months during hot summers if you run your AC frequently.

Some filters only need to be replaced once per year and vary based on the size and type of mesh. A brand new filter will allow you to accurately program your Pro1 t705 thermostat.

6. Replace Batteries

Battery-powered Pro 1 t705 thermostats require two AA batteries to run properly. You will need to replace your batteries after 10-12 months. Pro 1 t705 thermostats have a low battery icon that tells you when it’s time to replace the batteries before it’s too late.

Your Pro 1 t705 won’t work without batteries if it is solely battery-powered and not hardwired. However, it may work at a limited capacity if it is hardwired and uses batteries as a backup. In that case, you will still need to replace the batteries to make the t705 work at full capacity.

Do You Need Your Thermostat Repaired or Reprogrammed?

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Summing It Up

Reset your circuit breaker if your Pro 1 thermostat isn’t working after a power surge or outage. Inspect the wiring on your t705 and rewire it or hire a professional if it is faulty. Clean the wires beneath your thermostat face with compressed air if it is dusty or caked with debris to make it work.

Put two new AA batteries in your Pro 1 t705 if your thermostat displays a low battery icon. Replace your air filter if your cooling and heating briefly run then shuts down or if you inspect it and see that it is dirty. Pull the thermostat away from its sub-base, remove the batteries, put them back after 10 seconds, and reattach the thermostat.

That is how you reset a Pro 1 t705, and it is helpful when you don’t know what else could be wrong. Hire an electrician or HVAC professional if you have limited wiring experience and the wiring is faulty. Pro 1 t705 thermostats are reliable, and they are typically easy to troubleshoot when there is a problem.

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Nick Durante
Nick Durante

Nick Durante is a professional writer with a primary focus on home improvement. When he is not writing about home improvement or taking on projects around the house, he likes to read and create art. He is always looking towards the newest trends in home improvement.

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