Diagnosing A Dead Thermostat

By Tyler Karstensen on 05/22/2019

Bad Thermostat Symptoms

The thermostat one of the most important pieces in your HVAC system.The thermostat is a device that lets you turn the heating and cooling system on and off, as well as change the specific temperature in the house. HomElectrical put together a short guide on how to tell if a thermostat is going bad.  

 

Furnace or Air Conditioner Refuses to Start

It is a bad sign if your HVAC system does not turn on at all. Go to the thermostat and change the system from heating to cooling, back and forth.  If you get no response from your heating and cooling system, the thermostat could be faulty. This may also be a larger issue, and we would recomend getting a professional electricain to inspect your home's central air conditioning unit. 

 

Air Conditioner Runs Constantly and Won’t Turn Off

A faulty thermostat can cause an HVAC system to run all the time. This issue could be a simple wiring issue, meaning you wont have to replace your thermostat. Take the face plate off the thermostat to make sure the wires are intact and connected to the appropriate node.

Thermostat Does Not Respond to Temperature Change

Your HVAC system should immediately respond to a temperature change on the thermostat by turning the fan on. Test this by changing the temperature higher or lower by 5 degrees, you should hear a click, and then the air conditioning should turn on. If the heating and cooling system don’t fire up the you may have a faulty thermostat. 

The HVAC System Short Cycles

In some cases, your heating and cooling system will startup but never actually reaches the desired temperature. A good sign of a system short cycling is if the thermostat temperature does not match the room temperature. Your home may never reach the desired temperature until the problem is fixed

 

Some Simple Fixes

The problems above can be caused by any number of reasons. If you’re not sure what the problem is, or do not feel comfortable diagnosing it yourself, we recommend hiring an HVAC professional to help solve the issues.

 

Check the Batteries

 

Most modern thermostats rely on a battery for power. The batteries should be located behind the faceplate. If the thermostats screen still won’t turn on, you may need to replace your thermostat. 

Check the Circuit Breaker

 

Most modern HVAC systems are connected to your breaker box. The problem could the as simple as your breaker has been tripped and no power is being sent to your thermostat or heating and cooling system.

 

Check the Wiring

There are wires that connect your HVAC system with your thermostat. These wires must be connected to an appropriate node inside the thermostat to function properly. Turn off your HVAC system and take the faceplate to check the wires. Reconnect any wires that may have become disconnected and check your furnace again.

 

Clean that Mechanical Thermostat

Older analog thermostats use a bi-metallic strip that expands, and contracts based on the increase or decrease of temperature. The thermostat can stop working if dust collects on the inside. To clean it simply pop off the faceplate and blow off the inside with a can of air duster. 

 

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Learn more about HVAC by checking out these blogs below:

  1.  What is the difference between a Line Voltage and a Low Voltage Thermostat
  2.  How to Replace an Analog Thermostat 
  3.  Can I Use a Smart Thermostat in My Home?

 

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