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The Most Common Thermostat Problems and Their Solutions

Thermostat Problems
Under-performance of cooling or heating systems are mostly due to problems in the thermostat. For A/C troubleshooting, it is necessary to understand and solve these issues at the earliest.
Yash Gode
Last Updated: May 6, 2018
With central cooling or heating systems controlling temperatures at our homes, offices, shopping malls and even car and buses, the relevance of air conditioning systems and their maintenance has grown. The thermostat is one very vital component of all controlled temperature systems, and most of the system's problems can be attributed to issues in the thermostat.

The Thermostat Explained

Have you ever noticed air conditioning systems switching on and off by themselves? If you have a conventional electric oven, you must have observed that heating coils stop heating after some time. Why does this happen and what causes it? It happens because in both the cases mentioned above, there is a manually set temperature, which when attained, a device turns the system off, thereby stopping the flow of heat, so that a desired set temperature can be maintained. The device responsible for regulating the temperature is called a thermostat. So now, you can imagine that any problem with thermostat can cause a lot of discomfort. Without it, one will have to control the temperatures manually, whenever we feel too hot or too cold. So, let's quickly take a look at the problems and troubleshooting for a thermostat.

Most Common Thermostat Problems
First signs of problems with a thermostat include drop in performance of the temperature regulating system, and can make you feel too warm or too cold. Before calling out an A/C repair professional, it can be worthwhile to look at the thermostat yourself.

The most important factor you need to see is the place of installation. If you have the thermostat mounted on a wall with a high thermal coefficient, then such a device will fail to offer you comfortable temperature, as it will never react properly to the air in the room. But instead, it will clock the temperature of the walls. Similarly, if they are installed at places where there's direct sunlight or near an outside door or window, you will face a similar problem. Ideally, a thermostat's installation should be close to where the filter is, so that it can sense and react to the temperature in the air handler.

Make sure there is no hole or empty space behind the thermostat. Such a space can feed cool or warm air currents to its back. If you happen to notice a big hole at the back of the thermostat, you can stuff some insulation in this hole, like cotton gauze, or cover it with non-conducting tape. On mechanical (non-digital) thermostats, a heat anticipator is installed which needs to be set in accordance to the current draw on the thermostat circuit. This anticipator may need periodic manual adjustments with the help of an amp meter to get a proper setting.

Any kind of thermostat is always susceptible to dirt problems. The dust and grime that builds up inside the thermostat will hinder its working. What you can do is open up the front panel of the thermostat and clean the dirt using a small and light brush. Dust especially (and very carefully) around the contact points; that's where the dust causes most of its problems.

This is the most obvious problem. If your thermostat is old and not working as it used to, just replace it. As with all electronic or mechanical equipment, the thermostat will work worse the older it gets. And replacing parts won't help much. You'll just end up periodically replacing something or the other. Rather buy a new one and be done with it.

Power Supply
Some thermostats, mostly digital ones, use battery power for their functioning. It might be a simple case of the battery getting discharged, or a malfunctioning of the battery recharging system. Inspect the batteries and replace them if required. Some digital thermostats are designed for AA batteries, or if there are back lights, then they may use AAA batteries. In case you think that the charger has some issues, make sure to check the power switch circuit breaker in the battery charging circuit.

Most thermostats used in homes are powered by 24 volts AC, and this power is derived from an air handler and heating split system. Such thermostats are known to be equipped with a power stealing technology. In such cases, it is better to first check the circuit breaker meant for the air handler and make sure it is not tripped. It is not uncommon for people to forgo these circuit breakers and that is when they think the thermostat is out of order.

Loosely-wired or Miswired
HVAC systems are not to be trifled with. A lot of people get the notion that they can fix a broken thermostat, as it is just a matter of twiddling with a few wires. Chances are, they'll end up smoking the control boards or the transformer. Unless you have good experience in HVAC installations, I strongly advise that you get your thermostat looked up by a professional. Because you're not just messing with a piece of electrical equipment that costs a decent chunk of money, you're risking your own self while tinkering with it. In fact, you'll often come across forums that deny any DIY help to people who are new to this, because they know the risk involved. And while we're at it, in no case will you open up the thermostat while the power is still on. Make you you trip not only the outer breakers, but the inner home breakers as well.

Programming Defects
These days, most A/C systems are equipped with programmable thermostats. The biggest problem in such devices is their RAM-like programming chips. These thermostat chips lose their programming whenever there is an abrupt power failure. To get rid of this situation, you need to reprogram the chip, but it will meet a similar ending whenever there's another power failure. These days newer programmable thermostats are available which have a ROM memory which does not perish with a power failure. But, if the old system does not support these new programmable thermostats, the only option is to go for conventional battery powered ones.

These are the major problems which are highly prevalent in air conditioning systems. Even though temperature control systems have become technologically superior, improper usage and non-standard installation can damage the system and cause trouble.