My Air Conditioner Smells Bad. Why?

Why does the air conditioner smell so bad? If you have asked yourself this question at some time or you are doing it right now, it is because you have suffered the unpleasant problem that your air conditioner "stinks" as soon as you turn it on.

My air conditioner smells bad; when I turn on the air conditioning, it just feels like my whole house is rotting.

This is a phrase our HVAC technicians come across and have been told many times, and their answer is always the same... the air conditioning machine, by itself, does not produce odors. What happens is that the machine, if it is a duct air conditioning unit, it usually sucks in the air from the upper part of the false ceiling. So, if there is some kind of odor accumulated there when the unit is turned on, it will move and disseminate it throughout the house, giving the feeling that it is our air conditioning machine that is causing the smell.

So, does the air conditioner never smell?

No, our air conditioning machine can smell horrible, but this smell, except in very specific and rare cases, is never produced by the machine. It is generally produced by other factors and then ends up affecting the air conditioner. Let's see what factors can affect and produce that bad smell in our air conditioning unit.

Dirty filters

Air conditioning filters are one of the few things or the only ones that require periodic maintenance done by HVAC maintenance professionals. This maintenance, while is very simple to perform, is not to be DIYed. Proper maintenance and filter cleaning tend to help us to keep our air conditioner in the best possible conditions, avoiding possible breakdowns, reducing consumption and also, avoiding and eliminating those unpleasant odors that we absolutely hate.

And why do the filters smell?

The filters do not usually smell. The filters perform their function of filtering air and trap in the mesh they are made of, a multitude of particles that exist in the air, preventing these particles from reaching the inside of the unit. While the dust is stopped from reaching the inside of the unit, it gets stuck on the filters, and when it accumulates, things start getting worse, and it gives away a rotting smell.

But what happens when the filters are not cleaned properly?

Well, what happens is that the filters get clogged and saturated, thus preventing them from performing their function properly and causing that dirt to be passed little by little into the interior unit and therefore filling it with dirt. This dirt in combination with the humidity that is produced in the exchanger and the indoor fan (especially when operating on cold mode), will cause a multitude of bacteria and fungi to proliferate in these places. This is what gives rise to the typical smell of "humidity" with touches of vinegar. Hence, proper air conditioning maintenance can save you quite a lot of trouble and make sure your home remains livable and free of these unbearable odors.

Dirty cooling fan and exchanger

As mentioned, when an air conditioning unit does not receive proper maintenance, however small the maintenance need is, it has consequences in the long run. This lack of maintenance includes not cleaning the filter of the air conditioner which causes accumulated dirt to pass through the filter and accumulate in the rest of the indoor unit, in places that are much more complicated, as well as expensive and difficult to clean.

Two of the places or "pieces" that get very dirty when this happens are the cold exchanger and the indoor fan, which literally fill up with "filth." This filth, together with the humidity produced by the unit in cold mode, produces in these fans and exchanger as "a wet paste" where bacteria and fungi proliferate, producing that unpleasant odor that produces an unbearable smell as soon as the unit is turned on. But, after a while, when the room becomes adequately cold, it disappears.... wrong! This smell does not disappear, go away or is eliminated, but it becomes hard to smell because when cooling and producing water droplets (condensing moisture) this humidity creates a protective barrier that prevents us from smelling it. But once the air conditioner stops cooling and the moisture condenses, the odor returns with increased intensity.

Drain of the indoor unit

The drain of the indoor unit can also "produce" odors. Let us see some of the reasons why this happens.

All the air conditioning units have a drain because they all condense moisture when they "produce cool air." They function by condensing the humidity and generating water. This water must be expelled somewhere from inside the unit, and this is where the drain of the indoor unit comes into play and drives this water out of the unit.

The drain does not have enough slope

A fault in the design of the drain of the indoor unit is that it does not have a sufficient slope to ensure proper drainage. If this is the case, water accumulates in the tray of our indoor unit, which after a certain time rots and creates a bad odor.

Other possible causes that your air conditioner smells bad

The above points are largely responsible for the fact that an air conditioning unit smells bad, but there are other factors that although being less common and sometimes very rare, can also produce bad smells, we will cite some briefly.

• Smells that are transmitted from the chamber of the wall of the house to the interior of the house (bad sealing of the hole and insulation of the smelling chamber).
• Air fresheners inside the air conditioning.
• Our indoor unit (ducts) sucks air from the false ceiling, and there is some type of leak in the drain of the house.
• Our air conditioning unit sucks air from the false ceiling of a neighbor's house.

In any case, if you feel the slightest hinge of a bad odor in your house, give Comfy Climate a call and get your AC unit fixed by a professional HVAC maintenance service.