Having problems with your HVAC? Try these thermostat troubleshooting tips before calling a technician!

Modern programmable thermostats for HVAC systems have come a long way from the basic dial models that required the user to manually set the temperature. These new designs can help save hundreds of dollars on utility bills by “remembering” what temperature your home needs to be during different times of the day. This ensures that your HVAC unit only runs when needed and, more importantly, your household always keeps comfortable.

While programmable devices have become smarter and more precise, some people have found them to be more complicated to use. A small disconnect in how to properly program a thermostat can lead to several issues, including poor HVAC performance and system failure. Of course, not everyone owns a programmable thermostat – and there are several reliable manual models that work very efficiently as well.

No matter the design of your current model, if you are having problems with your HVAC, the culprit could be the thermostat itself. Whether it’s electronic, mechanical or a modern “learning” design, it will be worth the effort to read our troubleshooting tips before calling a professional technician.

Problems with Heating and Cooling

If you are having recurring heating or cooling problems, try these tips:

  • An older thermostat design, especially the ubiquitous circular or rectangular “mercury” models can be very sensitive. Dust can play a role in their efficiency. If you own an older thermostat, consult the manual and try lightly dusting the exterior and interior with a cloth.
  • How old is your thermostat? Even the “newer” digital models will need to be replaced at some point. If your thermostat is 15 years or older, the wiring might be the culprit. Consider replacing it with a new, energy-efficient model.


  • Is it set for cooling/heating? Check to make sure that it is programmed in the correct mode.
  • Try resetting the system by turning the thermostat off and on again.
  • The fan mode is sometimes mistakenly turned on. Make sure that the fan is turned off.
  • Check the settings. If they appear to be correct, try a heating/cooling test by setting the temperature a few degrees above or below the current reading.
  • Have you checked the batteries? If your thermostat requires batteries, sometimes the solution is simply changing them out. You might also check the circuit breaker to make sure it’s not a power issue.
  • Check the wiring on the back and make sure that it’s not an issue with the connection.
  • The anticipator in your thermostat might require a simple adjustment. Open up the housing on your thermostat and look for the small metal tab situated next to a scale (reading shorter to longer). Try moving the anticipator to the “longer” setting, making adjustments one calibration mark at a time.

Recurring On/Off Cycles (Rapid Cycling)

If your HVAC system is turning on and off too frequently (referred to as rapid cycling) it might be a problem with your thermostat. Rapid cycling can also be attributed to debris and dirt within the components of your HVAC – another reason for annual maintenance. If your system is cycling too frequently, look into these options:

  • If you own a mechanical thermostat, remove the cover and make sure that the subbase is mounted level on the wall. The mercury switch inside won’t work properly if it is askew. This will compromise the accuracy of the temperature readings and can cause a rapid cycling issue. Refer to the manual for directions on how to properly level the subbase (which might simply require the tightening of the mounting screws.
  • Problems can arise if your thermostat is “ghost reading” a nearby temperature. Is the thermostat near a heat-producing appliance like a ceiling fan or large light fixture? A hot area like a window or door could also be causing the problem. Your thermostat should be placed in a central area, removed from major appliances and “hot” areas. It should be mounted at least five feet from the floor where it can get a true air sample.
  • Rapid cycling could also mean that there is a problem with the heating or cooling unit itself. Always check the filter to make sure that it isn’t dirty. During a heavy usage period, generally summer and winter, a filter should be changed at least once a month. A dirty filter or heat exchanger can obstruct the airflow of the HVAC, causing it to overheat and shut itself down. When the system cools, it will turn on once again only to shut down and repeat the cycle.

Knocking/Clicking Sounds

If you hear a recurring knocking or clicking sound coming from your HVAC, it could be a faulty relay. This would prevent the unit from getting the signal from the thermostat. In this case, you will need to call an HVAC technician to fix the problem.

Call the Experts

If you are still experiencing problems with your HVAC after using our troubleshooting tips, you should call in a professional technician to assess your system. Remember that the experts at Interstate Heating & Air Conditioning have the tools and experience to help you with all of your HVAC needs. Call us at 405-794-8900 today to schedule service!


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