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Thermostat Troubleshooting: 5 Common Fixes


It’s a bummer if your thermostat stops working on a steamy summer day, but there are some quick things you can check to see if your thermostat is faulty or just needs a quick fix. Here are our top 5 things to check when troubleshooting your thermostat.

Check For Power

The type of thermostat you have – digital or mechanical dial – will determine how it gets its power. 

“Most new thermostats are digital, some call them electronic,” says Keith Hill, manager of technical support at Minnesota Air. “They require a power source to operate. Some take their power from the furnace low voltage power supply – wired directly to the furnace ­– and some have batteries for their power supply. Some have both, wired power from the furnace and a battery backup so you don’t lose your programming during a power outage.” 

If you have a thermostat that uses batteries, weak batteries should be something to look at right away. A quick battery change and you may be back in business.

With wired thermostats, you’ll want to make sure that a circuit breaker isn’t tripped or a fuse isn’t blown. Keith says that wired thermostats may have a blank screen if the furnace power is turned off or the furnace circuit is tripped. However, he reminds homeowners to also be patient.

“Sometimes the thermostat is blamed as faulty when the air conditioner doesn’t start immediately on a call for cooling, but it could be a built-in time delay,” he says. “As a protection against short cycling, some thermostats have a built in time delay and sometimes the time delay is built into the air conditioner. Wait 3 or 4 minutes for the delay period to pass before condemning the thermostat.” 

Check The Calibration

If you have been noticing that your thermostat never really gets to your desired temperature, then you may have an issue with the calibration or placement of your thermostat.

According to the Department of Energy, the location of your thermostat can affect its performance. That’s because “a thermostat must be on an interior wall away from direct sunlight, drafts, doorways, skylights, and windows … where natural room air currents – warm air rising, cool air sinking – occur.” 

In fact, we’ve put together a whole guide to thermostat placement to help you out. 

Other issues may be with calibration, meaning the thermostat doesn’t seem to be operating at the correct set point.

“You have it set at 74 degrees, but it’s 76 in the house,” says Keith. “Some differential is normal, it’s called a temperature swing, but it usually is only one degree or fractions of a degree on modern digital thermostats. If it is consistently higher or lower than the set point, then recalibration or replacement is required.” 

Check The Thermostat Mode 

It may seem obvious, but make sure you check the mode you have your thermostat set at. If you want your AC to turn on, make sure it’s on ‘Cool,’ and if you want warmth, make sure it’s set to ‘Heat.’ You would be surprised by how many people accidently leave their thermostat on ‘Off’ mode waiting for something to kick on.

Check Thermostat Temperature Setting

Another obvious thing to troubleshoot, but equally as easy to overlook, is the temperature setting.

Keith says that on some digital thermostats, after you make a temperature change, you have to hit the ‘enter’ button or ‘done’ on the screen for the thermostat to accept the change.

“Many service calls have been the result of not completing that final step,” he says.

Are You Part Of An Energy Saver Program?

Finally, keep in mind if you have had a power saver switch turned on by your power company. An energy saver program is offered to customers by the utility or power company. They typically work by giving the consumers a discount on their energy use, and in exchange, the company has permission to shut your AC off during peak periods (hot days) – or if they have other reasons to lighten the load due to power supply problems.

Keith says this is something you would have signed up to be part of and you can tell the power company turned off your AC because the fan will be running but the air conditioner will not when they are controlling due to a peak power condition. 

“Some power companies have an electrical box with a light (located outside by the air conditioner) that indicates if you are being controlled,” he says.

So, if it’s a hot day and your thermostat seems to be acting up, try troubleshooting these simple things first and you may save yourself a call to a technician.

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