Karen Wiggins on June 24, 2015 97 Comments A thermostat is one of those things that you don’t pay too much attention to until it breaks. Usually, thermostats do their job quietly, in the background, without requiring much outside interference, but when it stops working, everybody in the house notices. When the temperature inside is suddenly freezing cold or burning hot, most homeowners will do just about anything to fix it and restore a comfortable environment. Before you call the repair man to fix your air conditioning or heating unit, make sure the thermostat isn’t the problem. Below, we outline some things you can do to check its functionality and ensure you have a working thermostat. Before anything, you need to determine which type of device you have and understand how it works. Electromechanical Thermostats Electromechanical thermostat devices are older and more basic than modern examples, operating on very simple mechanical principles. A strip of two different metals joined together rests just under the cover, sometimes in the shape of a coil. This strip, or coil, will expand and contract with the fluctuating temperatures, activating the contacts on either one or both sides of the metal. If the unit controls the heating and cooling functions, it will have contacts on both sides; if it only controls one option, it will only have a contact on one side. In a dual-controlled unit, this switch will tilt one direction if it is hot and the other if it is cold, creating contact with the appropriate side to activate the heater or the cooler to turn on. This system is sometimes joined with a mercury switch, which is a tube filled with mercury that also tilts as the coil expands or contracts, causing the mercury to move from one side to the other and thus opening or closing the points of contact. Electronic Thermostats Modern types of thermostats are electronic and function like a small computer. Often times these are programmable, allowing you versatile flexibility in how you set temperature controls, timers and preferences. Unlike electromechanical thermostats, which require manual adjustments, electronic versions allow you to set the temperature for a different setting when you sleep, wake up, return home and even for different days, such as on weekdays and weekends. This is a much more convenient setup than the simpler models, but it also means that there are more pieces that can break and maintenance work is more difficult and expensive. There are often inexpensive electronic models, making it often more feasible to simply replace your unit than try to fix it. Now that you can assess which type of thermostat you have, it will be easier to determine the problem. While some fixes require a trained repairman, there are several issues that you can resolve on your own. Here are some common problems and solutions that you may find helpful: Furnace Won’t Start Being caught in the cold winter months with a faulty furnace is a situation that nobody wants to be in, but there are things you can do to remedy the problem on your own. Here are some suggestions to try if your furnace won’t turn on: Check the power source, looking for things such as blown fuses, tripped breakers and dead batteries. Check for dirt, dust, spider webs and nicotine buildup. These can coat the inside of the thermostat and cause the mechanical and electrical components to malfunction. To clean, use a soft brush, like a clean paintbrush, to gently brush the interior components. Compressed air is also useful in cleaning out the thermostat. Check for loose screws and corroded or loose wires inside the thermostat. Be sure to cut the power before you remove the thermostat cover, and check the owner’s manual to ensure correct wiring schematics. While performing these simple fixes may not correct the problem, they can help you narrow down the issue to make it easier for the repair mechanic to quickly determine the problem and cause. Room Temperature and Setting Don’t Match Another function to check before calling a professional is whether the thermostat keeps the room at the correct temperature or not. To do this, tape a small thermometer on the wall next to the thermostat, being sure to place a paper towel behind the thermometer so that it won’t be affected by heat or cold transfer from the wall. Wait for at least 15 minutes to ensure that temperature is stabilized and giving a correct reading, then compare it to the reading on your thermostat. If the numbers are more than a degree apart, the thermostat is likely not giving an accurate reading. This is a very important factor to know when you speak with the repairman about the problem. Other Factors To Consider Some other factors that you should take note of when diagnosing your malfunctioning thermostat are listed here: Make sure the inside of the thermostat is clean. Check if the thermostat box is level, since being off-center can alter the accuracy of the internal component. Check your box’s location, since placement in direct sunlight or in front of drafty windows and doors can greatly affect correct temperature regulation. Determine if the anticipator is set correctly. If you have a mechanical thermostat, check for a little metal tab that is mounted to a round dial on the inside. First, try pushing the tab lightly in either direction to see if that solves the issue. If not, you may need to set it to the furnace’s ampere setting. This is most easily accomplished by consulting the owner’s manual or directions indicated on the unit’s service panel. Unit Won’t Turn Off or Constantly Switches Off and On Having a furnace or cooler that won’t turn on can be frustrating, but finding that yours won’t turn off can be equally difficult. Try these simple fixes to get your unit functioning properly again: Again, check for dirt and residue buildup. This is often the cause of many problems. Check to see if the box is level. Adjust the temperature higher or lower to see if that has any effect on the length it stays on or its likelihood of shutting off. Having a thermostat that functions correctly is vital to keeping your interiors comfortable and livable during any weather. Many of the problems require simple fixes and can sometimes be taken care of on your own, but more complicated issues will need the help of a mechanic or even require replacement. After taking a look at the problems and solutions listed here, you should be able to determine the difficulty of your issue and whether or not you’ll need a professional.