How do you know if you need a new thermostat?

Author: Jed Brakus  |  Last update: Sunday, August 10, 2025

If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.

How can I tell if I need a new thermostat?

Signs You Need a New Thermostat
  1. Heating or cooling system will not turn off or on.
  2. The temperature reading is incorrect.
  3. Recent spike in your energy bill.
  4. Frequent temperature fluctuations.
  5. Thermostat is 10 years old or older.

How can you tell when your thermostat is bad?

A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.

Does a new thermostat make a difference?

If you have an older HVAC system, you can optimize and extend its life by getting a thermostat upgrade. This will reduce further wear and tear, thereby eliminating the need for constant repair and other maintenance costs.

How do I test my thermostat?

Methods for Testing Your Thermostat
  1. Just Turn it On and Let it Work. One way to test your thermostat is to simply turn it on and see if it cools the room down. ...
  2. Get an Indoor Thermometer. Another way to test your thermostat is to use a thermometer. ...
  3. Use a Multimeter. ...
  4. What to Do if You Notice an Issue.

SYMPTOMS OF A BAD THERMOSTAT

How to reset a thermostat?

Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.

Can I replace my thermostat myself?

In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.

Do I need an electrician to replace a thermostat?

Yes, many smart thermostats are designed for DIY installation, and manufacturers typically provide step-by-step guides and videos. However, if your HVAC system is older or lacks proper wiring (like a C-wire), the installation might become more complex, and you may need professional help.

How much does it cost to replace a thermostat?

The average cost of a new thermostat, including installation, ranges in price from $50 to $500 or more based on several factors including the type of thermostat, labor costs, the complexity of the installation, and more.

Can a thermostat go bad without overheating?

One of the lesser-known issues is the polar opposite of overheating. Overcooling happens when the engine does not reach the right temperature for its normal function. In this scenario, the thermostat is stuck open and overflows the radiator with coolant, drastically reducing the engine life cycle.

Will you get a code if your thermostat is bad?

P0128 is an extension of OBD-II code P0 which indicates a problem with your car's coolant thermostat.

How many years should a thermostat last?

The lifespan of most home thermostats is 10 years. However, you may need to replace yours sooner as newer, more efficient thermostats enter the market. You may, for instance, want to replace a non-programmable thermostat with a programmable option.

How do I know if I have a bad thermostat?

One of the most obvious signs you need to replace your thermostat is when it doesn't do anything. If your thermostat display doesn't light up or respond when you press buttons or try to change the settings, you may have to replace it. Before assuming you have a broken thermostat, make sure it has fresh batteries.

Is it my furnace or thermostat?

Pay attention to how often your heating system cycles on and off. Frequent cycling could be a sign of thermostat problems as it struggles to maintain the desired temperature. If the system stays on for extended periods without adequately warming the house then the furnace might be working inefficiently.

What happens if I don't replace my thermostat?

Your AC and Heater Won't Start

If the thermostat's wiring becomes loose, it can break connections with your home heating and cooling appliances. This means that the thermostat isn't controlling the air conditioner or the heater.

How do you know if you need to replace thermostat?

If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.

Who to call to check thermostat?

If your wires are connected but your thermostat still isn't working properly, that means it's time to hire a professional. They'll open the thermostat and test the wires individually to see which one is faulty. Since messing with wires is dangerous, you'll want to contact a certified HVAC technician.

Can I just buy a new thermostat?

You can typically just replace the outdated thermostat with a new thermostat – assuming the latter is compatible with your HVAC system. There are a few things you should know, however, when upgrading your thermostat.

How do I know which thermostat to buy?

4 Simple Steps To Choosing The Right Thermostat For Your Home
  1. Step 1: Figure Out Which Thermostat Is Compatible With Your Heating And Air System Type. ...
  2. Step 2: Learn About (And Choose) Your Thermostat Type. ...
  3. Step 3: Choose Your Programming Options. ...
  4. Step 4: Install Your Thermostat. ...
  5. Looking For More Help?

How expensive is it to move a thermostat?

Moving a Thermostat: If the required wiring exists at the desired location, moving a thermostat may cost as little as $65. However, moving the unit can entail installing new wiring and cutting and patching drywall, so the project can cost up to $450.

How difficult is it to replace a thermostat?

Knowing how to install a thermostat can be a budget-friendly DIY project. All you need are a few tools such as screwdriver and voltage meter. You can choose to install an analog, digital or smart thermostat.

Can a home thermostat go bad?

Thermostats can go bad when the set temperature doesn't match the home's temperature. This is normal if you have a zoning system, but the temperatures shouldn't fluctuate on their own. This is a common sign that the thermostat may have reached the end of its lifespan.

Why is AC not blowing cold air?

First, check your filters and coils for dirt and debris that may be impeding airflow. Once you've cleaned the filters and coils, run the air conditioner with just the fan so that the ice accumulation can melt off. If the AC still doesn't blow cold air, it could be that refrigerant levels are too low.

Will resetting my thermostat fix my AC?

Any time you are having an issue with heating and cooling units, such as after a sudden power failure or after your children have had 'control' of the system while you've been away, resetting the thermostat should be the first thing you try when attempting to rectify HVAC system issues.

Previous article
Will soaking clothes in hot water shrink them?
Next article
How much does it cost to rewire a whole house?