By Michael Mankarious

Last updated: Jan 30, 2025

If you have an odor coming from your car's air conditioner that smells like old gym socks or (gasp) urine, then you have mold in your air conditioner system. Don't panic. Put away the air fresheners, we'll show you how you can fix it with Klima Cleaner Pro.

What's the cause of the musty air conditioner odor?

Every time you use your air conditioner unit, you are providing an opportunity for odor-causing mold and mildew to grow within your air conditioning system. To explain how this happens, a basic explanation of how the AC system works.

When the air conditioner is operating, it pulls moisture out of your cars interior through the evaporator coil, which is located underneath your cars dashboard. By pulling moisture from the air, the relative humidity is decreased allowing the air temperature to feel cooler. The moisture that is pulled from the air condenses and is drained outside the car. Ever notice a pool of water under your parked car on a hot summer day? That's the water that was drained from the system. This also happens to be the way home AC systems work.

Even though most of the excess moisture is drained from the car, moisture still remains on the evaporator coil and the box that the core sits inside of. As the air circulates around the evaporator core, dust and pollen in the air stick to the moisture buildup on the metal fins of the evaporator. Soon thereafter, mold begins to grow on the surface of the evaporator. This collection of grime and odor-causing agents begins to release unwanted odors and is the cause of the moldy smell coming from your air conditioner.

Remedies for your smelly air conditioner

One way to help prevent or at least reduce moldy smells is to keep the air conditioner in the fresh air setting. This keeps the air circulating around the evaporator, which helps keep it and the surrounding area dry, thereby reducing the chance of any mold from growing.

However, there are two disadvantages to this method. First, it's also not always convenient to switch to the fresh air setting in order to draw in hotter air to dry out the AC unit. It just might be too hot or cold to be worth this extra effort. It's also not economical.

Second, allowing fresh air to flow in increases the accumulation of dust, pollen and brake dust build up. Of course if you have a cabin air filter you don't have to worry about that since it will trap the pollutants before it reaches the evaporator area.

Another possible solution is to spray a disinfectant like Lysol into the ventilation system or have your car treated with ozone or another similar system. However, this process does not affect any dust, pollen and other contaminants that have accumulated on the evaporator, which could also contribute to air conditioning smells. While it may disinfect any mold, mildew and bacteria, the results are usually short-term.

Last but not last, you can have your system treated by the dealership. They will use Klima Cleaner or a similar product and may charge $150 and higher for this service. This is the most effective solution, but it can be expensive.

Solution: Klima-Cleaner

As we found, the best solution is to have the dealership treat your air conditioning system for you. However, it's quite expensive. If you are a do-it-yourself-er, you can use the same product they use. Applying Klima Cleaner Professional effectively washes the evaporator core and the evaporator box that it's housed in removing any odor-causing agents. Klima Cleaner's effective foam solution emulsifies the debris build-up on the evaporator core so it's cleaner and will run more efficiently.

Another significant benefit is the result of cleaner and fresher interior car air.

For those who are highly sensitive to chemicals, rest assured that Klima Cleaner is a water- and salt-based cleaner so chances of any skin reaction is extremely minimal.

HVAC Cleaner Application

Apply Klima Cleaner exactly as directed on the product label taking caution that it may be best to have it applied by a certified mechanic if you are unsure about applying the product yourself. If you're confident in applying it yourself, learn more about Klima Cleaner Pro application here.

It's best to apply Klima Cleaner every six months. The easiest way to remember is to apply it every time you change your oil. We also suggest you change your cabin's dirty air filter at the same time for optimum air conditioning performance and the freshest, cleanest air.

And don't think that Klima Cleaner is only for the spring and summer. Applying it in the winter is also important whether you live in an area that snows or rains. If you drive in the winter, you've probably used your air conditioner setting in conjunction with the heat setting to dehumidify the interior. If so, the evaporator core is susceptible to the same issues as in the warmer months.

Summary

Detailing your car is a full system process involving the treatment of every aspect of the car. An application of Klima Cleaner Professional as part of your detailing regimen will improve the performance of your air conditioning system and improve the indoor air you breathe in your car.

Ready to eliminate your AC odor? Shop Klima Cleaner Pro →