The thermostat is a device familiar to every homeowner. And when it stops working, everyone in the household notices.
If the heating or cooling suddenly turns off, one of the first things you should check is the thermostat.
First, make sure it is set to “heat” if you want warm air and “cool” if you want cold air. Then, check that the fan is set to “auto” and the temperature setting is higher than the room temperature (for heating) or lower than the room temperature (cooling). Learn more thermostat troubleshooting steps.
If your settings are correct but your thermostat still has problems, there are a couple of other things you can try before calling in the professionals.
Dust and dirt are often the cause of inefficiencies and inaccurate temperature readings.
Many homes still have older thermostat models, known collectively as electromechanical thermostats. Old-fashioned mechanical thermostats have two strips of metal that form a single bimetal strip.
The bimetal strip contracts or expands depending on the surrounding temperature.
Colder temperatures contract the coil, causing contact with the air conditioning unit. Warmer temperatures expand the strip, causing contract with the heating system. If you don’t have heating and cooling, there will only be one contact on one side.
Newer thermostats are electronic (or “digital”) and work much like small computers. They are normally labeled as “programmable” or “smart.” These thermostats allow much more customization, but when something breaks, you will most likely need professional help.
The inside workings of electronic thermostats are complicated and repairs and replacements are more expensive. Unlike electromechanical thermostats, however, you’ll never have to adjust the anticipator or dust off the metal coils and contact plates. When used correctly, an electronic programmable thermostat can save you around 10% on your heating and cooling.
Learn the best way to program your thermostat for fall and winter savings.
When was the last time you cleaned your thermostat? Probably never. If your furnace or air conditioner won’t start, try opening up your thermostat and giving it a little cleaning.
Regularly cleaning your electromechanical thermostat will keep it operating accurately and efficiently.
Since figuring out how to open up the thermostat housing can often be the most difficult and frustrating part, watch this video to learn how to correctly open your thermostat:
Once you have successfully opened your electromechanical thermostat, you’ll want to clean out all the dust, dirt, bugs, and buildup. Use the instructions below to clean your heat sensor, and if possible, your exposed contact points and switch contacts.
What you’ll need: a clean, soft paintbrush and a clean dollar bill. Maybe a Q-tip and alcohol.
Turn your thermostat up until the contact point closes. Now wiggle a soft piece of paper such as a dollar bill between the contact points. Blow it clean.
Use a soft, clean paint brush to brush away any dust and buildup around the metal coil. If the brush isn’t able to get between the coils, you can try sliding dollar bill (or soft paper) back and forth. Blow it clean.
If your thermostat has them, you can clean the switch contacts with a Q-tip moistened with some rubbing alcohol.
After you have cleaned the inside of your electromechanical thermostat, it’s a good idea to use a leveling device to make sure it is exactly level on the wall.
Learn more about the science of electromechanical thermostats from Mr. Wizard:
If you are thinking about replacing your thermostat with a more functional and energy-efficient model, contact the experts at Service Champions. We are Certified Nest Installers and can install any type of thermostat you desire.
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