Posts made in January, 2019

How to Troubleshoot a Faulty Thermostat 

»Posted by on Jan 7, 2019 in Uncategorized | 0 comments

Nowadays, heating and cooling systems are controlled by a thermostat that maintains the desired level of temperature. The thermostat will then send a signal to the system when to turn on or power off during the times that no one is using the system or if the desired level is already achieved.  

 Faulty Thermostat

Most of the thermostats are low-voltage; they reduce the line voltage from 120 to 24 or 12 volts. If you notice that your system isn’t functioning well, the HVAC company will most likely find out that the problem is the thermostat (even though you have a new air conditioner) and that it needs to be fixed. This article will tell you how to troubleshoot a thermostat before it finally breaks down.  

Understanding Common Furnace Thermostats 

To know how to troubleshoot your thermostat, you should have at least basic knowledge about it. Thermostats fall into two categories: line voltage and low voltage (the focus in this article). Traditional thermostats like a mercury bimetallic thermostat describe how an analog type works. It has heat anticipator, contact and bimetallic strip or coil.  

The mechanical contact thermostat doesn’t use mercury contact switch, it uses a simple mechanical contact. This is not yet programmable. It has modes for cooling and heating and fan positions. The digital thermostat uses electronic controls, which is not also programmable. The electronic thermostat is like the digital one, but better. It’s fully programmable and will even allow you to customize the temperature of different days.  


  1. The System Doesn’t Produce Cool or Warm Air If you try to turn on the system but it fails to do so, it might be because of the thermostat. Do not instantly assume that the problem is the furnace of the unit itself. There are a lot of cases that this happens which is caused by no electrical current that reaches the thermostat. The possible reasons why this happen are dirty components, blown fuse or tripped circuit breaker, bad battery and loose wires.  One of the things you can do is resetting the circuit breaker. If the thermostat is dirty, clean the components gently especially the switch contact and the bimetallic coil. Make sure to tighten any loose screw terminals and check for wires that are disconnected.
  2. Failure in Setting the Desired Temperature Another sign of a malfunctioning thermostat is when the desired temperature is not set. The AC or furnace unit is okay but doesn’t set your desired temperature. Some of its causes are crooked thermostat or incorrectly set heat anticipator. To fix this problem, remove the thermostat’s cover and loosen the screws. Level it, retighten the screws and replace its cover.
  3. The Unit Turns Off and On Frequently The HVAC systems doesn’t frequently turns on and off, so when it does this, it’s probably because the electrical connections of the thermostat are not making consistent and clean contact, this is called short-cycling. To fix this problem, remove the cover of the thermostat and clean the components. Pay attention to the switch contact and bimetallic coil.  
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