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How to Get Mildew Smell from Car AC Out

If your car's AC has a mildew smell, it can be unpleasant and hard to get rid of. This guide provides effective tips and methods to eliminate it.

A fresh, cool breeze flowing from the air conditioning (AC) vents is a welcome relief on hot summer days. However, sometimes that breeze carries an unpleasant odor akin to mildew. This distinct smell can indicate a problem with the AC system, specifically a clogged drain pan. Understanding the root cause of this issue and knowing how to remedy it can help restore the AC system's functionality and eliminate the unpleasant odor. In this article, we will delve into the working of an AC system, explore the reasons behind the mildew odor, and provide practical steps to address the clogged drain pan.

The Role of the Evaporator Unit

To comprehend the issue at hand, let's begin with a brief overview of the AC system. At the heart of the system lies the evaporator unit, a crucial component responsible for cooling the air. When the AC is in operation, the evaporator rapidly cools down. Air passes through the evaporator's numerous fins, resulting in chilled air being expelled from the vents. On hot and humid days, condensation forms on the evaporator due to the stark temperature contrast.

Car AC Evaporator

The Drain Pan and Its Function

As condensation forms on the evaporator, it gradually drips down into the drain pan located beneath it. Under normal circumstances, this collected moisture is channeled through a hose and eventually expelled onto the street. However, when a clog obstructs the drainage path, moisture becomes trapped in the drain pan. The stagnant water creates an environment conducive to the growth of algae-like organisms, which emit a mildew odor. When the AC system is in operation, the odor is carried by air and blown out through the vents, causing the unpleasant smell to permeate the surroundings.

Addressing the Issue

To resolve the problem of a mildew odor emanating from the AC, it is necessary to locate and eliminate the clog in the drain pan. Here are some steps to follow:

1. Identify the Hose. Begin by positioning yourself underneath the vehicle and locating the hose leading to the evaporator drain pan. If you require assistance in finding it, consult the vehicle's manual or seek professional guidance.

2. Clear the End of the Hose. Inspect the end of the hose and clean it thoroughly, removing any mud or debris that may be obstructing the flow of moisture. Sometimes, this simple action can resolve the issue.

3. Addressing Deeper Clogs. If the end of the hose is not clogged, the blockage may be further up the hose or in the base of the drain pan itself. In such cases, it is advisable to seek professional assistance to accurately locate and clear the clog.

4. Patience is Key. Once the clog is removed, it is essential to understand that it may take a couple of days for the algae-like organisms to dry up completely, leading to the disappearance of the mildew odor. Therefore, exercise patience during this process.


The presence of a mildew odor emanating from the AC vents is an indication of a clogged drain pan in the evaporator unit. Understanding the functioning of the AC system and the role of the drain pan helps us grasp why this odor occurs. By following the steps mentioned above and ensuring the proper drainage of the condensation, it is possible to eliminate the mildew odor and restore the AC system's functionality. Remember to exercise caution during the cleaning process and seek professional assistance when necessary. With a little effort and patience, you can enjoy fresh, odor-free air conditioning once again.

1 comment:

  1. My Tahoe has been to the shop 6 times in six weeks for the air conditioner. Problem is I am in it $1,200.00 and it still don't work. They can't seem to find the leak. They have put a new compressor and lines and fan clutch and condensor in it and it still leaks somewhere but where? They have put die in it and still they can't see where it's going.


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