My Thermostat Is Not Reaching the Set Temperature, Why?

One of the most aggravating things that can happen is when something you own doesn’t serve its solitary purpose. This is especially true when it comes to your thermostat and its inability to reach the room temperature that you set.

If your thermostat is not reaching the set temperature then there is an underlying issue, below I am going to highlight some of the most common issues that cause this problem – be it misplaced, dirty, unlevel, or the wiring could be loose, vents could be clogged, or a simple recalibration could do the trick.

Misplaced Thermostat

A thermostat being placed in the wrong location is an easy mistake to make, and although it is more common to see with DIY jobs, sometimes licensed technicians put them in a bad spot too.

A bad spot in this scenario is anywhere external forces affect the desired temperature reading on the thermostat. This will always affect the thermostat’s ability to reach the set temperature.

Locations to Avoid

1. Above or below a vent

By placing a thermostat above or below a grated vent you are potentially allowing the outcoming cold air, or warm air, to interfere with the temperature on the thermostat. 

2. Around windows

If your thermostat is placed on a wall that gets a lot of sunlight throughout the day the thermostat will read a higher temperature than what the air actually is which causes the heater or air conditioner to shut off before the set temperature is actually reached.

3. Near Lamps

Traditional lightbulbs ten to put out a large amount of heat. For this reason, you should avoid placing your thermostat near, or above a lamp.

4. Next to a furnace or other appliances

Appliances such as a furnace or a water heating system put out large amounts of heat – for this reason, your thermostat should never be placed on a wall that has an appliance on the tither side of it.

Dirty Thermostat

Your thermostat may trap dirt and grime inside over time which can lead to interrupted or faulty connections between wires and terminals.

For this reason, I recommend you make sure to routinely remove the cover of your thermostat and gently dust out the inside with a soft cloth or a q-tip.


Thermostats snap into their mounting plate and connect to the wired portion through a series of pins. If the thermostat is unlevel it could interfere with the integrity of these connections, causing it to misread and misadjust the temperature so that the thermostat never reaches the set temperature.

Loose Wiring

A lot of wires call the inside of a thermostat home and over time they have a tendency to become loose, which can cause faulty performance from the thermostat.

Every couple of months you should expose the wiring to your thermostat and ensure that all of the terminals are tightened down and have a good solid connection.

Clogged Vents

HVAC systems rely heavily on their ability to freely be able to take air in and move it out. If any exhaust, vent, or section of ductwork is clogged, this will interfere with your HVAC system’s ability to properly perform and reach the set temperature of the thermostat. Another drawback to these types of problems is their negative effect on indoor air quality.


Electrical problems can lead to your thermostat needing to be recalibrated. This can be caused by a low battery level or more commonly, a power outage.

You can ensure that this is the problem by taping an accurate thermometer next to the thermostat and leaving it there for 10 minutes. If the temperature on the thermostat and thermometer are different then you need to call a professional to come out and calibrate the thermostat.


The thing about an HVAC system is that it is 100% interconnected – for this reason, it can sometimes prove difficult to determine the exact problem. 

Above is a list of the most common causes of this issue – clogged vents, loose wiring, unlevel or dirty thermostat, or maybe it needs a simple recalibration. Whatever the issue may be, you can assure the right fix the first time with a service call to a locally licensed technician.