A/C Fault Code & Reduced Output

[N800MRG]

Hi Guys,

I have the following fault code, paired with reduced airflow from the vents (around 50% what it used to be) and a slightly musty smell when starting the car after it has been sat. I have tried changing the pollen/cabin filter, but this didn't help. I also ran a couple of cans of AC cleaner/disinfectant through the system.

Any ideas?

Thanks in advance,
Marcus

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[allenh427]

Hey this is a complete guess, but I had a 370z that I took in to get an underbody spray /sealer. They sealed over the AC drain and it got a nasty smell and didn't work as well. Yours might be clogged.

 

[XtremeMaC]

Check this area for blockages. That's where the A/C system pulls fresh air from.

 

[N800MRG]

I've checked the drain, and under the scuttle trim where the A/C system pulls fresh air from, nothing out of the ordinary from what I can see.

The only issue I can find, is that the airflow arrow on the Pollen/Cabin Filter points the wrong way. I've tried two different filters, one genuine BMW, the other aftermarket. It's almost like all the filters are designed for LHD cars, so when fitted into a RHD car you have to flip the filter the other way to fit into the housing, but this means the airflow arrow faces the front of the car...

The slanted edge of the filter points towards the centre of the car in both LHD and RHD variants, which should theoretically mean there's two different filters, but there isn't from what I can find. My car came back from service with the filter crushed into the housing the 'wrong' way, but this meant the airflow arrow was pointing the 'right' way...

I appreciate this is a mainly US-biased forum, so it's unlikely anyone has ever come across this issue, but if anyone could shed some light on this, it would be much appreciated.

 

[N800MRG]

I've checked the drain, and under the scuttle trim where the A/C system pulls fresh air from, nothing out of the ordinary from what I can see.

The only issue I can find, is that the airflow arrow on the Pollen/Cabin Filter points the wrong way. I've tried two different filters, one genuine BMW, the other aftermarket. It's almost like all the filters are designed for LHD cars, so when fitted into a RHD car you have to flip the filter the other way to fit into the housing, but this means the airflow arrow faces the front of the car...

The slanted edge of the filter points towards the centre of the car in both LHD and RHD variants, which should theoretically mean there's two different filters, but there isn't from what I can find. My car came back from service with the filter crushed into the housing the 'wrong' way, but this meant the airflow arrow was pointing the 'right' way...

I appreciate this is a mainly US-biased forum, so it's unlikely anyone has ever come across this issue, but if anyone could shed some light on this, it would be much appreciated.

Update, I have found a genuine BMW filter that appears to multi-directional (airflow arrows point both ways). I have ordered it along with some Liqui-Moly A/C System Cleaner. Will update the thread with my results once they arrive.

 

[Mason]

Unlikely that the filter direction really matters

 

[XtremeMaC]

I mean you can run it without the filter to test it out.

Sounds like maybe the blockage is in the unit itself or some faulty something something..

 

[N800MRG]

Unlikely that the filter direction really matters

I mean you can run it without the filter to test it out.

Sounds like maybe the blockage is in the unit itself or some faulty something something..

I tried removing the filter, and the airflow goes back to normal. If I leave the A/C running on full, then slide the filter into the housing, I can feel the airflow drop off substantially, if I pull the filter back out, normal airflow returns.

Obviously you're always going to get some restriction from a microfilter, but I'd say that the airflow drops by 50% or more when I put the filter in...

The new, multi-directional filter is arriving early next week, fingers crossed that provides less restriction?

 

[Mason]

But is it cooling while the filter is out?

 

[N800MRG]

But is it cooling while the filter is out?

Yes, cooling/heating has never been affected, only airflow.

 

[XtremeMaC]

That's weird.. either you're too sensitive or there's still something else in there.

Anyhow, remove filter. Reset error message.
Put existing filter back in. With some filters direction do matter. Check if you have Air Flow arrow on it .. then check to see if error comes back..

Vs

 

[Mason]

The higher efficiency the filter, the less airflow will be output. Big time misunderstanding for the average consumer.

Try a less dense / less efficient filter even

 

[N800MRG]

That's weird.. either you're too sensitive or there's still something else in there.

Anyhow, remove filter. Reset error message.
Put existing filter back in. With some filters direction do matter. Check if you have Air Flow arrow on it .. then check to see if error comes back..

Vs

The top photo is what I've got at the moment, so currently the air flow arrow is pointing towards the front of the car. The bottom photo is what I've ordered.

The top filter would be fine in an LHD car as the arrows would point towards the cabin. As the RHD car I have is just a mirrored version of the LHD car, with the filter fitted the correct way in the housing, the airflow arrow is facing the wrong way.

So my guess is the fact the filter is fitted 'backwards' is causing the restriction...

 

[N800MRG]

The higher efficiency the filter, the less airflow will be output. Big time misunderstanding for the average consumer.

Try a less dense / less efficient filter even

I currently have the cheapest, flimsiest filter I could find in there, as I bought it to test the issue.

The problem is that the airflow arrow is pointing the opposite way to what it should be. This is the only theory I have as to why the drop in airflow is triggered by sliding the filter in and out of the housing...

 

[Mason]

The problem is that the airflow arrow is pointing the opposite way to what it should be. This is the only theory I have as to why the drop in airflow is triggered by sliding the filter in and out of the housing...

It could be different for cars / your country but in my experience, airflow arrows don’t really matter if there isn’t any electronic polarization in the filter. It’s really hard to tell without cfm numbers but it sounds like you’re on the right track

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