Bad Cabin Air Filter Symptom

A cabin air filter is designed to prevent unhealthy and harmful bacteria or particles from entering the vehicle’s passenger cabin. 

A new or properly cleaned cabin air filter only allows fresh air molecules to enter the heating and air conditioning system of an automobile which keeps the inside environment of a vehicle safe and healthy for passengers. But with time, the cabin air filter gets old and its performance deteriorates. 

Therefore, a cabin air filter must be replaced or cleaned periodically to achieve the purpose for which it has been designed. There are a few bad cabin air filter symptom associated with an old or poorly performing cabin air filter which are given below and have been discussed in detail one by one.

Bad Cabin Air Filter Symptom

Following is comprehensive list of Bad Cabin Air Filter Symptoms

  • Reduced airflow from the HVAC system
  • Strange odors inside the vehicle
  • Dust and debris blowing into the cabin
  • Poor defrost performance
  • Increase in allergens and irritants inside the vehicle
  • Diminished fuel efficiency, air conditioning performance, and cause of foggy windows
  • Strange noises coming from the HVAC system

Reduced airflow from the HVAC system

Several types of cabin air filters are available in the market. Famous and common cabin air filters are activated carbon cabin air filters and HEPA (high-efficiency particulate air) cabin air filters.

Reduced Air Flow in HEPA cabin air filter: HEPA is a kind of mechanical air filter that does not allow particles of size larger than its pores to enter the heating and air conditioning. The particles (dust and other allergens etc.) that do not enter the HVAC system of the vehicle are collected at the exterior of the filter. 

With time, the filtered debris and dust particles increase and fill in the pores of the cabin air filter. In this way, the area or passage for the fresh air molecules to enter the filter pores decreases and hence the incoming airflow reduces.

Reduced Air Flow in activated carbon cabin air filter: Activated carbon or activated charcoal cabin air filter are a kind of chemical air filter that has an activated carbon layer also known as charcoal which reacts with the air contaminants (volatile organic compounds, pollen particles, etc.) and binds with them. 

This phenomenon reduces the passage for air molecules to enter the heating and air conditioning system of the vehicle and hence reduces the airflow inside the passenger’s cabin.

Strange odors inside the vehicle

Strange or unpleasant odor in the case of HEPA filters: Two types of cabin air filters are used commonly. HEPA cabin air filters are the most common ones whereas activated carbon cabin air filters are also used in several vehicles. 

The HEPA cabin air filter being the mechanical air filter is not able to stop foul and unpleasant odors from entering the HVAC system of a vehicle. 

So, if an unpleasant or foul odor is entering the HVAC system from the outside environment, then it is not a symptom of a weak or bad cabin air filter. But in a few cases, a HEPA cabin air filter can become the source of bad odors when it gets old. 

This is because moisture and other dirt particles filtered at the exterior surface of a cabin air filter mix with each other and stimulate bacterial growth. If this is the case, a filter then must be cleaned or replaced to get rid of such unpleasant odors. 

Although, few cabin air filters have antimicrobial properties that prevent bacterial growth and keep foul odors away.

Strange or unpleasant odor in the case of activated carbon or activated charcoal cabin air filter: Activated carbon cabin air filter is a kind of chemical air filter which unlike a HEPA cabin air filter can also prevent foul or unpleasant odors from passing through it. 

With time, the activated carbon binds with the molecules of gaseous particles and the surface of the cabin air filter gets covered by a layer of those entrapped molecules. Hence, the efficiency of such filters decreases with time and their ability to prevent foul odors from entering the system diminishes. Such filters cannot be cleaned and reused so therefore they must be replaced.

Dust and debris blowing into the cabin

A cabin air filter is designed to prevent dust particles and other pollutants from entering the HVAC system of a vehicle. Different types of filters are available in the market but the most common ones have activated carbon cabin air filters and HEPA cabin air filters. 

All these filters are rated on some standards such as MERV (Minimum Efficiency Reporting Values), MPR (Microparticle Performance Rating), FPR (Filter Performance Rating), and beta rating. 

A cabin air filter with the lowest rating filters out the fewest particles whereas the one with the highest rating prevents almost all unwanted particles from entering the HVAC system. 

Hence, if dust and debris are blowing into the cabin, it can be said that the installed filter might be of low ranking on a given standard. The second reason for dust and debris to enter the system can be an old cabin air filter whose sides are not properly seated in their place. 

Poor defrost performance

If the cabin air filter is not clean and clogged up with dust and other pollutants, it will not allow the appropriate and required amount of airflow through it.

 In the case of low airflow into the heating and air conditioning system of a vehicle, the air conditioning system becomes colder and colder and frosting starts to happen. Therefore, an old air filter will affect the defrosting performance of the HVAC unit of the vehicle.

Increase in allergens and irritants inside the vehicle

The air inside the vehicle’s passenger compartment must stay fresh and this will only happen if the heating, ventilation, and air conditioning system of the vehicle is working appropriately and efficiently. 

If proper ventilation is not being carried out due to the blockage of air at the cabin air filter, dust, and other pollen or allergic particles will start to accumulate in the passenger compartment of the vehicle. Therefore, if someone is not feeling at ease in a vehicle, the condition of the cabin air filter must be checked.

Diminished air conditioning performance & cause of foggy windows

An appropriate and compatible cabin air filter must allow air molecules to enter the HVAC system of a vehicle with almost no restriction. But a filter clogged with dust and other particles will not be able to do so and to meet the airflow requirement, the engine would need to put in more work. 

This extra work takes more power from the engine’s crankshaft and hence the mileage and fuel efficiency of the engine decreases. Additionally, when a cabin air filter is not clean, the airflow into the system decreases and disturbs the airflow balance across the system. 

Due to this the air conditioning and ventilation performance of the system starts to fade away. Furthermore, a poorly performing heating, ventilation, and air conditioning system will not be able to maintain the humidity requirements of the passenger area of the vehicle which might make the windows foggy and unclean.

Strange noises coming from the HVAC system

Although noise generation from cabin air filters is not a common phenomenon it may happen in some cases due to the following reasons. 

If the cabin air filter is not seated properly at its place, the air will enter the HVAC system from its sides and will make the process noisy. Therefore, if the HVAC system is noisy, the cabin air filter must be checked for its proper seating or installation.

The second reason for noises being generated from the HVAC system is the clogged cabin air filter. A cabin air filter whose pores have been blocked by filtered dust and other pollutants will not allow air to pass easily. This phenomenon will generate whistling and strange noises from the HVAC system of the vehicle.

Concluding Bad Cabin Air Filter Symptoms

A bad cabin air filter symptoms are discussed in details above and symptoms like bad odor, poor air quality, poorly performing AC system and foggy windows are all common found symptoms of bad cabin air filter. 
These issues can also be caused by other factors so you may need to work very comprehensively to solve these problems. If you have any question do message us or make a comment about it.

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