recirculation air filter

[slicky rick]

i was just wondering if our cars have a recirculation cabin air filter. i know we have a pollen filter to check the air going into the cabin from the outside. what happens if we always have the ac set at recirculation mode? does the air still pass through the same pollen filter located in the front trunk near the wiper beffore it goes to the evaporator? i have an s class that has a filter inside the cabin that filters the ac air in recirculation mode and it gets dirty fast. Im just thinking if the air in recirculation mode goes straight from inside the cabin to the evaporator, the evap will get dirty fast... seems very unlikely for a $100,000 car

[Loren]

i was just wondering if our cars have a recirculation cabin air filter. i know we have a pollen filter to check the air going into the cabin from the outside. what happens if we always have the ac set at recirculation mode? does the air still pass through the same pollen filter located in the front trunk near the wiper beffore it goes to the evaporator? i have an s class that has a filter inside the cabin that filters the ac air in recirculation mode and it gets dirty fast. Im just thinking if the air in recirculation mode goes straight from inside the cabin to the evaporator, the evap will get dirty fast... seems very unlikely for a $100,000 car

Item 2 is your pollen filter. It does the same process as the Mercedes filter.

[slicky rick]

hi loren, great to hear from you. thanks for indicating that however i wonder how the air in recirculation mode gets filtered before enterring the evap? from the diagram i can see that the pollen filter cleans air coming from the outside - recirculation mode is off. Does it also clean the air in Recirc mode? merc has 3 seperate filters - one for outside air(similar to item 3 in diagram provided) - recirc off, one for inside air-recirc mode on, and one charcoal filter for removing smell from air coming from either source...

from the way it looks on the diagram, the item 2 is exposed to the outside air and is used only when air from the outside is brought in to cabin

[ADias]

I doubt that the polen filter is in the loop when recirculation is engaged. What's the point of constantly filtering, internal (supposedly clean) air anyway? In addition, recirculation should be used as least as possible.

[RFM]

The pollen filter is only for outside air because the flap under the filter is closed when REC. is engaged. Anyway, the filter should be replaced on the regular maintenance schedule because he always is exposed to the outside air, independent of the AC/HEATER/VENT. system actual position. I would further follow up ADias counsel concerns the REC. position.

[slicky rick]

major reason why recirculation is almost always on here where i am is the pollution in the streets. if recirc is not activated all the smoke and the smell will go in the car. now the supposedly clean air inside the car is not the case again where i am. As i have pointed out my S Merc has a recirculation filter inside the cabin. this one gets dirty quite fast i should say. i clean it more than 3 times a year. If we all agree that there is no filter for recirculated air can someone point out to me where the system sucks in the air in recirculation mode? i would like to adapt a filter there similar to the filter used for window type airconditioners used in the house. 3M filtrete would me my filter medium. hope someone can point me to the right direction. just a preventive measure to lenghten service life of my evaporator.

[ADias]

Slicky Rick: In recirc mode there is no overt air input. You are breathing closed cabin air. Of course, there's always some air creeping in from the outside, but less than when recirc is off.

The pollen filter, stops large particulates but not gases or smells.

Your S-Merc cabin fllter does not renew the air, just cleans it from particulates. Are you sure that that filter is not used by external air. The fact that the filter is inside the cabin does not mean that it is strictly used in recirc mode.

[slicky rick]

hi adias, yes pretty sure that the filter cleans air being sucked by the system from inside the cabin in recirc mode. the filter in my mb is located below the dash in the passenger side footwell. it is very easy to clean and you can hear and feel the air being sucked in by the ac system from this area when in recirc mode. the outside pollen filter is located in an area similar to our p-cars, inside hte engine compartment. when recirc is off you can hear air being sucked in from the external filter, when recirc is on a valve is closed and air being introduced to the system comes from the passenger footwell area i mentioned. I am pretty sure the system in our p cars are similar. recirc mode sucks in air coming from inside the cabin and it closes a flap that leads to the polen filter we all know is located in the engine compartment.

i can only imagine how fast my evap would get dirty if there was no filter in recirc mode. it will be like the system in my 80's old cars where the evap input is simply exposed to the air inside cabin and pushed through the evap for cooling..