How to Troubleshoot a Faulty Thermostat?

Quite often the problems with a heating or cooling unit can be traced back to the thermostat. And it’s advised if your HVAC system is not working properly, to start troubleshooting by checking the thermostat. Some of the problems can be easily fixed. For example, the thermostat could be just out of adjustment. Or the batteries could be dead. If these don’t fix the problem, check for the following symptoms to understand the potential issues.

how to troubleshoot a faulty thermostat

The System Doesn’t Produce Heat or Cooling

If your HVAC system doesn’t turn on at all, there are a few thermostat problems that you should consider before assuming that the furnace is to blame. In some cases, it could be just that there’s no electrical current reaching the thermostat.

Possible causes for this include:

  • tripped circuit breaker
  • blown fuse
  • open connections in the thermostat
  • the components of the thermostat are dirty

Here are the repairs for the mentioned issues:

  • restart the circuit breaker
  • get a new fuse instead of the burned one
  • check for loose connections
  • remove the thermostat and gently clean the components
  • check also for any loose screw terminals

The Thermostat Doesn’t Control the Temperature

If the system is running but is failing to set the temperature to the desired level, the problem could also be with the thermostat.

It could be the cause of the thermostat being mounted in a crooked way. To fix this issue, loosen the screws that hold the unit to the wall, readjust it so it’s leveled correctly, and retighten the screws.

Another possible cause is that the heat anticipator is not set correctly. Again, to fix, just readjust it properly.

The Furnace Cycles On and Off

This is usually the cause of electrical connections inside the thermostat not producing clean, consistent contact. However, also keep in mind that on bitterly cold winter’s days, it’s normal for the HVAC system to frequently cycle on and off. Because at this time the temperature outside is a lot colder than the desired temperature inside.

But other issues to look for in this case are dirty components and the incorrect position of the heat anticipator.

To fix these issue clean the components and adjust the heat anticipator. When cleaning the components of the thermostat, pay especially more attention to the bimetallic coil and the switch contact surfaces.

If none of these fixes work, it could be that the thermostat is outdated. Sometimes, it’s not worth the time and effort to fix it and much easier to just buy a new thermostat.

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