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Do Home Thermostats Go Bad?

June 21, 2017

Wondering if your thermostat can go bad?

While a thermostat doesn’t have a set lifespan, on average, you can expect them to last at least 10 years. After a decade, thermostats may start malfunctioning due to aging wiring or dust accumulation.

In this article, we’ll share signs your thermostat is bad and how to troubleshoot a malfunctioning thermostat.

4 signs your thermostat is bad

Sign #1: Your thermostat has no power or is unresponsive

If there’s no change in your home’s temperature when you adjust the temperature, or the display is unlit or unresponsive, your thermostat may be broken or the batteries need replacing.

Sign #2: Your heater or A/C won’t turn ON

Is your heater or A/C not turning on? It could be a wiring defect in the thermostat the prevents electrical signals to be sent to your cooling/heating system.

Sign #3: Your A/C or heater runs constantly and won’t turn OFF

If your heating/cooling system runs constantly and won’t turn off, it could be that the wiring is frayed or that the thermostat is miscalibrated.

Sign #4: Room temperature and setting don’t match

A more subtle sign of a broken thermostat is when room temperatures don’t match. Now if your home is zoned, then temperature differences between rooms is normal. But if your home hasn’t been zoned, fluctuating temperatures in different parts of the house could point to a faulty thermostat.

How to troubleshoot a bad thermostat

Have you noticed any of those tell-tale signs? Follow these 5 steps to troubleshoot a bad thermostat...

Step #1: Make sure thermostat is on the right setting

OK, this is an obvious step, but make sure your thermostat is set on “heat” if it’s winter and “cool” if it’s summer.

If your A/C or heater is constantly running, your thermostat may just be set to “ON.” You should set your thermostat to “AUTO” so that your cooling/heating system isn’t constantly running (in “AUTO” mode, the blower will only blow air out of the vents when your system is cooling/heating the air).

Step #2: Turn the thermostat up or down 5 degrees

Try one of these steps (depending on the season):

  • If it’s summer, set the temperature 5 degrees lower than normal

  • If it’s winter, set the temperature 5 degrees higher than normal

When you turn the thermostat up or down, you should hear a click. Wait a few minutes to see if your supply registers blow out air or if your return vents suck in air.

Step #3: Replace the batteries (for electronic thermostats)

If you have a digital thermostat, try replacing the batteries to see if that fixes the problem. You should be replacing the batteries in your digital thermostat every year.

Step #4: Clean the thermostat (for mechanical thermostats)

If your thermostat is one with a little lever that moves the temperature, you have a mechanical thermostat. Over time, they can start to malfunction because of dust.

Take off the thermostat cover and dust the inside with a small brush or cloth.  

Step #5: Check and test wires and wire connections

You can try removing the thermostat cover and checking the wires to make sure they’re all firmly connected to their respective mounting screw.

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 up 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.

Need thermostat help from a professional?

Contact Advanced Air to schedule a thermostat repair. We’ll send one of our trusted technicians to your home and get your heating/cooling system working in no time.

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