How to Check a Home Thermostat with a Multimeter

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The HVAC system in your home can be composed of many different elements. When one of those elements does not work correctly, the whole system can start to have problems. Therefore, how do you check when a problem is taking place?

Is there anything you can do yourself to stop a total breakdown? 

If the furnace signifies the heart of your home’s heating system, consider the thermostat as the brain at the back of the whole operation. Keep in mind that your thermostat not just offers the needed controls required to run your furnace. It also controls when and how your furnace delivers heat throughout the day. That’s especially true if you spend the extra money on getting a programmable thermostat. 

You see, a sudden thermostat failure could leave your entire furnace non-operational. That will leave your home in the cold. Unluckily, assessing and testing thermostat failure could be a big problem because of the common symptoms often shared and other HVAC problems. 

That’s where testing a home thermostat with a multimeter comes in. In today’s post, let’s take a closer look at how a home thermostat works and the best ways to test it using a multimeter. This article will also highlight the common problems that could take place during a faulty thermostat.

Are you ready? Without further ado, let’s dive in! 

Common Symptoms of a Faulty Home Thermostat

A malfunctioning home thermostat generates some problems to tell homeowners it’s time for a replacement. Regrettably, such symptoms sometimes feel like comfort problems that result in homeowners thinking it is a cooling or heating equipment issue.

Your home thermostat is a probable cause of those problems. If you don’t know how to determine if your home thermostat is going bad, here are symptoms for you to consider.

  • Short cycling

A faulty home thermostat could also cause your entire furnace to start up and shut down in a fast sequence. Typically referred to as short cycling, that issue could cause massive and costly damage to your furnace.

What’s more, the majority of short cycling issues involving the thermostat are typically caused by malfunctioning wiring and bad thermostat placement. 

  • Wrong temperatures

Have you ever thought about why your home feels cooler or hotter than usual? If your house still utilizes an older thermostat, such temperatures may be wrong. Remember that older thermostats need calibration to run accordingly, or else the thermostat’s temperature settings could drift warmer or colder than your preferred setting. 

Do you have a new thermostat? Then it might be installed too low on the wall to read the temperature or installed in the wrong location, like on the exterior wall. Fixing such problems could help preserve your home’s thermostat and furnace’s overall functionality.

  • No-heat condition 

Any of the problems below could make a no-heat condition to your home thermostat:

  • Damaged wiring. Corroded, frayed, or burned wiring could also stop your thermostat from working appropriately.
  • Corroded contacts. Corrosion from leaking alkaline batteries could stop the contacts between the battery and thermostat from working right. Once you dispose of the batteries, you can use a paper towel to remove loose corrosion and use a cotton swab submerged in white vinegar to clean off the contacts.
  • Incorrect setting. Make sure you double-check the thermostat and ensure you did not set it to “cool” if you wanted “heat.”
  • Dead batteries. This is the common culprit of no-heat conditions caused by a home thermostat. Does the display show blank? That’s a typical sign of a dead battery. You can change the dead batteries for new replacements and test the home thermostat to make sure it works. 

Testing a Thermostat with a Multimeter

You need to check the heating element before jumping in to check the thermostat. Check details like the response of the electrical circuit to the thermostat and more with the help of digital tools. 

The open and grounded heating elements could bring our various tests. Hence, being certain about the measurements is necessary. Having a digital multimeter may come to be very convenient for you. 

Here are the necessary steps you need to follow when testing a thermostat with a multimeter.

  1. Check the terminals 

Check the terminals and find any power supply. Always keep the power turned on for measurement. If it’s working properly, it will give you a reading of 240 volts on every terminal. If you don’t find any or lower reading, check the power source and the high limit for the current.

  1. Stop the lower thermostat 

Rotate the dial to the lowest limit conceivable. Once done, higher up the thermostat in temperature. That will offer you a clear idea of where the issue lies.

  1. Set the prongs 

You need to set your prongs to the thermostat’s terminal 1 to get the readings you need. Ensure the multimeter is connected with the heating element along with the other prong. Once the power supply is on, you will receive readings without any delay. 

Do you find readings around 240 volts? It means the thermostat is getting enough power supply. Adjust the locations of the prongs to terminal 2 and check your readings again. It should then match on both the terminals. If not, think of it as a faulty component. 

  1. Check the lower thermostat 

Begin by changing the dial from the main thermostat to the lowest likely temperature settings. Set the lower thermostat’s dial as per the maximum limit. Set the prongs on the terminal once you’re done, and the red wire is present on the lower heating element. 

When the power is on, you’ll receive a reading. It should be about 240 volts to affirm that your thermostat is working well. 

Adjust the location and set it to terminal 2. Do you find similar readings? Then your device is working well.  If you can’t find any deflection, you’ll end up replacing both the thermostats. 

Final Thoughts

Above are the major concerns that are extremely prevalent in air conditioning systems. Although temperature control systems have become highly advanced, wrong use and non-standard installation could ruin the system and cause problems.

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