Pollen Filters-Airflow arrow question

Draeger · 25 Nov 2012 at 16:25

Just replaced my pollen/cabin filter on my 4007. Old one doesn't seem to have any airflow arrows marked on it so I'm not sure what way the new one is meant to sit as it has an arrow and 'Airflow' marked on it.

Do I fit the filter with the arrow pointing down or up?. I found a video online showing the replacement process for a 2010 Mitsubishi Outlander (identical car - different badges)and the guy said the arrows were supposed to point down towards where the spinning impeller in the fan unit sits, is that correct?. It looks a bit strange as to me the fan being at the bottom is blowing air UPWARDS towards the vents in the dash so if the arrow was pointing downwards surely thats facing against the direction of the airflow and the wrong way?. Or do the Airflow arrows on these filters generally point towards where the air is flowing from?.

Here's how I've got it just now:-

Tom_ed1987 · 25 Nov 2012 at 16:43

I would guess the arrows should point towards the fan. The fan airflow exit is perpendicular to the axis of rotaiton.

ThriceNightly · 25 Nov 2012 at 20:06

you have it the right way round

Howard · 25 Nov 2012 at 20:15

The arrows indicate, and should point in the direction the air is going, I.e. towards the cabin.

MissChief · 25 Nov 2012 at 23:40

Turn the fans on full blast, put hand in to see which way air is flowing, insert pollen filter correct way?

Howard · 26 Nov 2012 at 08:15

It's obvious. If the fan is at the bottom, blowing upwards towards the ducting that leads into the cabin, then the filter needs to be flipped round so the arrows point in this direction.

Nomisf · 26 Nov 2012 at 12:56

Howard said:
It's obvious. If the fan is at the bottom, blowing upwards towards the ducting that leads into the cabin, then the filter needs to be flipped round so the arrows point in this direction.

In most fluid/gas systems, inline filters occur before the pump unit to protect it from debris. So i guess if the fan is below it, then the filter is fitted right at the moment ?

Jonnycoupe · 26 Nov 2012 at 13:00

Howard said:
It's obvious. If the fan is at the bottom, blowing upwards towards the ducting that leads into the cabin, then the filter needs to be flipped round so the arrows point in this direction.

Not really obvious if you have it wrong.

Big clues:
1. the recirculation door is above, this is an air inlet to the HVAC.
2. its an centrifugal type fan on the blower, air enters the centre and it thrown outwards in all directions, the air then ducts around the fan bowl to the exit duct.
3. Filter is typically pre fan to prvent debris getting to the motor and making a racket.... ie a leaf.

Howard · 26 Nov 2012 at 13:13

Jonnycoupe said:
Not really obvious if you have it wrong.

Big clues:
1. the recirculation door is above, this is an air inlet to the HVAC.
2. its an centrifugal type fan on the blower, air enters the centre and it thrown outwards in all directions, the air then ducts around the fan bowl to the exit duct.
3. Filter is typically pre fan to prvent debris getting to the motor and making a racket.... ie a leaf.

Well I was going on his description. He said the blower is at the bottom, and the dashboard ducting is at the top, therefore the airflow would be in that direction.

I can't identify all the components and system layout from that close-up photo anyway.

Anyway, I did say 'if'

MOOGLEYS · 26 Nov 2012 at 13:21

MissChief said:
Turn the fans on full blast, put hand in to see which way air is flowing, insert pollen filter correct way?

+1 Remove the filter and whack it on full and you will be able to feel the airflow direction. Fit the filter with the arrow pointing that way.

Jonnycoupe · 26 Nov 2012 at 13:24

That is definately the right way in the picture.

Draeger · 26 Nov 2012 at 13:43

Cheers folks, much appreciated. I looked up the Peugeot TIS and found this:-

Hard to tell exactly but it looks like there are arrows on that filter in the diagram which are pointing downwards.