If you're having problems with your facility's heating or cooling equipment, the first thing to check should be the thermostat. These devices control HVAC system operation and, if they fail, can make it look like there is something wrong with your heating or cooling equipment. Since thermostats are easily accessible and relatively inexpensive to replace, they should be among the first things to check if you have HVAC trouble. Keep the following tips in mind to determine if you need a thermostat replacement.

Signs of a Failing Thermostat

You may be able to still get some service out of a failing thermostat, but if the device doesn't work properly, you should consider immediate thermostat replacement. Some signs of thermostat problems include:

• HVAC system won't turn on: 

  The most obvious sign of a bad thermostat is that the HVAC system in your building won't turn on or respond to the thermostat. You should be able to turn on your heating or cooling system from the thermostat, or change operation back and forth from heating to cooling. If you make changes at the thermostat and get no response whatsoever from your furnace, air conditioner, or heat pump, it could mean the thermostat is bad.

• Thermostat doesn't respond to changed settings: 

  When you make temperature settings at your thermostat, it should almost immediately respond to those changes. In most cases, the thermostat will produce a small clicking sound when the changes are made, then the heating or cooling equipment will start. If this clicking sound doesn't occur, or if the system doesn't come on shortly after the changes are made, the thermostat may need replacing.

• HVAC system short cycles:

  Short-cycling occurs when your HVAC system shuts off too early and fails to complete a full heating or cooling cycle. This results in ineffective heating and cooling and means that your indoor environment will not be comfortable.

• Thermostat loses programmed settings: 

  Programmable thermostats are designed to maintain settings over a long period of time. If your thermostat keeps losing these settings, it could indicate a need for thermostat replacement.

Thermostat Troubleshooting

• Check the screen: 

  Check the screen of the thermostat and make sure that it is lighted. A blank or unlighted screen could indicate a thermostat failure.

• Check the batteries: 

  Many modern thermostats rely on battery power to operate. If the screen is blank or unlighted, a battery change could solve the problem. Other thermostat malfunctions could also be the result of bad batteries. Change the batteries and recheck function of your heating or cooling system.

• Check the settings: 

  Changes in settings could be caused by weak batteries or thermostat malfunction. Make sure that the thermostat is set to provide either heating or cooling, as needed, and that programmed set-points are correct. Also make certain that the temperature settings are appropriate for the season. If you have the settings too high in the summer, for example, the cooling system won't come on and work as expected.

• Check circuit breakers: 

  Check the circuit breakers to make sure they haven't tripped. Look for breakers on the HVAC equipment and at the main breaker box. If they have tripped, reset the breakers and test your thermostat and HVAC system again.

• Check thermostat location: 

  The location of your thermostat can affect how it functions. A thermostat in direct sunlight, for example, will sense warmer temperatures and will respond as if the indoor temperature is hotter than it actually is. Large holes or openings behind thermostats could also cause inaccurate temperature readings. Make sure the thermostat is mounted in a position where it isn't too hot or too cold.

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