5 Reasons Your Air Conditioner Smells Bad and What To Do About It

Picture this. It’s the first heat wave of the year and you’re cranking up the ole A/C, but there’s a problem: Your air conditioner smells bad.


Maybe it’ll go away if you give it some time.

…and maybe it won’t.

Chances are, if you’re here, it hasn’t gone away. So what do you do about it?

Is the air conditioner smell a bad thing? Is it a simple fix? Should you run your system or turn it off? Is it bad enough you need to call someone to fix it? How much is it going to cost?

All these concerns hit you all at once and it can get overwhelming.

Nobody likes unexpected problems.

But our first goal is going to be identifying the smell. After we know the source of the problem, we’ll be able to see what we can do about it.

Why Your Air Conditioner Smells

There are all kinds of reasons why your air conditioner smells bad. Some of them are simple fixes, and others are more complicated.

We’ll let you know when you can solve the problem yourself, and when you’ll need to call a certified HVAC technician, like Precision Temperature.

Let’s dive in:

1. Smells like something is burning

If your air conditioner smells like it’s burning, the chances are it probably is.

This is one of worst problems you can have, and we’re tackling it head on.

Your air conditioner is a machine and has a ton of moving parts. Any one of those parts could be faulty from the blower motor to the wiring, or some other mechanical issue.

The key here is to turn off your system and stop using it immediately.

The last thing you want is to have fire when you aren’t home.

If the smell continues even after you’ve turned it off, contact the fire department. Use judgement here of course, only do so if you suspect the unit is still actively burning.

Chances are the problem will stop when the air conditioner is turned off. To make sure there’s no power, turn off the disconnect box on the wall near your outdoor condenser.

2. AC smells like cigarettes

We’ve covered a major issue, now let’s talk about an easy one.

As with the burning smell, if your air conditioner smells like cigarettes, the chances are it is cigarette smoke.

Air Conditioner smells like cigarettes

If you or a loved one frequently smoke in your home, the smoke likely filtered through your ductwork. Those scent particles then embed themselves into your air filter.

When you turned on your air conditioner, those particles were knocked loose and sent through your vents and back into your home.

To solve this problem, change your air filter. This should be done twice a year at a minimum anyway. Once in the winter and once in the summer.

Ideally, you’ll change your air filters once every 90 days.

3. It smells like something died

Surprise, surprise, if your air conditioner smells like something died, it probably did.

“But I’ve checked everywhere.”

There’s a few places you might not have checked for the pesky critter who had the audacity to die in your house.

The first could be the air handler of your air conditioner. This piece of equipment is what cycles air through the house and runs your air through the air filter.

This doubles as your furnace in a traditional air conditioning system, or is in place of it if you have a heat pump, which provides both heating and cooling.

The furnace/air handler is likely located in your garage, a closet, or your attic. All three are favorite places of pesky critters.

But there’s one other place the rodent could have died, and that’s in your ductwork.

Depending on the location of your air handler, you would be able to remove the faceplate and get at the critter, but if it’s in your ducting you’ll have to call a professional.

If you notice the smell is stronger near one vent than another, you might try removing the vent and checking if you can see the animal and/or reach it.

If not, an HVAC technician will need to come to locate and remove the problem.

4. Air conditioner smells musty

Your air conditioner smelling musty could be by far the worst of the problems listed.

While a burning smell might prove to be the most dangerous, it’s usually quickly diagnosed and solved.

Mold and mildew are sneaky enemies. They take time to develop, and because of this, you may grow steadily used to the smell.

You may only discover the issue if a friend or family comes to visit, or you get a particularly strong gust of the scent.

If mold is present, that means you have a water issue. It could be a leak in your air conditioning system or it could be completely unrelated.

When water damager is involved, repairs could get expensive. The good news is, if you have homeowner’s insurance, you should only have to pay the deductible.

Be aware, though, that homeowner’s insurance usually only covers the cost to repair the damage to your home, and not the cost of any appliances that need replaced.

If the source of the leak is discovered to be your air conditioner, and it’s still under warranty, replacement of your unit may be covered subject to the conditions of the warranty.

But what if it’s not? Or what if you have an old unit and the warranty has long since expired?

That’s where regular preventative maintenance becomes crucial.

Bi-annual system inspections, called tune-ups, keep your air conditioner and furnace working properly and discovers potential problems before they become major issues.

5. It smells bad in general

Maybe you can’t pinpoint the bad smell.

It doesn’t smell like a dead animal, mold, or cigarettes, and nothing is burning. What now?

It just smells like dirty socks or general stink.

Air Conditioner smells like stinky socks

This air conditioner smell is likely caused by a dirty evaporator coil or clogged condensate drain.

If it’s the former, you can help by spraying your condenser with a hose to clear out dirt and debris (turn off the disconnect first). But you should consider a A/C tune up for a professional clean.

If it’s the latter, you’ll definitely need to call a technician to be sure your lines aren’t damaged in the process of cleaning them.

What To Do About It

There are really only two solutions for each of the common air conditioning problems listed above:

Try to do it yourself or call a professional.

When your air conditioner smell problem could be solved on your own, we’ve offered possible solutions above. But for all other issues, it’s best left in the hands of a professional.

Even if you’re a DIYer, unless you’ve been trained to work on air conditioning systems, you should call your local HVAC company.

Precision Temperature is here to help you with any of your heating and cooling needs in San Diego.

Give our office a call today at 619-588-5321 and one of our friendly staff will be able to assist you further.

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