Why Does My Thermostat Say Check System?


Your home’s HVAC system is a complex mechanical network that is responsible for keeping your home climate-controlled and comfortable for your family. This includes keeping it warm in the winter and cool in the summer. There are many components that are crucial in the operation of your air conditioner and furnace, but it’s hard to imagine one as important as your system’s thermostat. In today’s blog, we’re going to take a look at thermostats: how they work, what they do and potential issues.


The thermostat is basically the command center and acts like a minicomputer. It senses what the temperature is and then sends out a signal to your system to either fire up the furnace to increase the temperature or to the air conditioner to cool down the air. It can be programmed to fit your schedule and, using wireless and smart device technology, can be operated from remote. There are two basic kinds of thermostats: digital and mechanical. Today, most new thermostats are digital/electronic, which feature electronic sensors that can detect temperature changes and adjust the temperature accordingly. Mechanical systems operate with two metal strips that expand as they heat/cool and trigger an electric circuit to your heating and cooling system.


There are several potential issues that could cause your thermostat to malfunction. If you have a digital readout thermostat, you may even see a check system message on the screen. Chances are that this message is simply a reminder that your system has not been serviced in a while and it’s time for a checkup. But it could mean there is an issue that needs attention, or your thermostat could even stop working correctly. Here are some indicators and causes:

  • Desired temperature is not being reached. While this could indicate a thermostat malfunction, also check the location of the thermostat and make sure it is not in direct sunlight.
  • Age of thermostat. Mechanical components get old and break down, it’s just that simple.
  • Dirt buildup and bad batteries. Dirt buildup around the sensors in the thermostat housing can cause malfunction. Also, periodically change the batteries in the thermostat to ensure proper operation.


Armstrong Plumbing, Air & Electric has serviced the Lubbock, Texas area since 1934 and our professionally licensed and trained HVAC technicians are ready to help keep your home’s heating and cooling system in tip-top shape. During these winter months, your furnace needs to be operating in peak condition, so make sure to give us a call today to schedule furnace maintenance, which will also include inspecting your thermostat. And don’t forget to ask us about our Armstrong Service Agreement Plan. ASAP coverage includes bi-annual furnace inspections/tune-ups and discounts on parts and labor.