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Discussion Starter #1 (Edited)
Anyone got any ideas why my interior fan makes a angry grinding sound when I brake hard? I have checked out some of the other threads on this forum ref worn fan units, but none of them mention anything related to braking.
 

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How do you know it's the fan? Switch the ventilation knob to '0' and see if it stops. If so, it's the fan, otherwise it's something else.
 

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Well, the fan still runs on a slow speed when it's set to 0 - it's a saab safety feature - fresh air comes in, old air goes out the side vents.

I would guess the fan could make a noise if it were worn to the point that braking caused it to move in it's housing and rub against something. That being said, I have no idea if there is even anything there to rub!
 

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Discussion Starter #4
cdaly said:
How do you know it's the fan? Switch the ventilation knob to '0' and see if it stops. If so, it's the fan, otherwise it's something else.
This problem only happens occassionally, and it does stop when I switch the vents to '0'. Also I have experienced the fan grinding sound on very cold mornings. One of the guys on another forum recommended spraying WD40 in through the air micro filter chamber, anyone tried this with the same problem?
 

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Discussion Starter #5
TheRedBaron said:
Well, the fan still runs on a slow speed when it's set to 0 - it's a saab safety feature - fresh air comes in, old air goes out the side vents.

I would guess the fan could make a noise if it were worn to the point that braking caused it to move in it's housing and rub against something. That being said, I have no idea if there is even anything there to rub!
Red Baron, I thought this possible if the plastic fan blades had come loose on their bearing, but it's a shot in the dark without getting into the dash, which I'd rather avoid!
 

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Hi

This happened on my 1990 900i as well but it only happened either when I braked very hard or when I was braking when going down a steep hill. It only stopped if I turned the vent setting to 0 i.e. the fan switched off. I never did find out what the problem was as I sold the car but I suspected that the fan itself was loose and when braking it somehow moved on its bearing and was either touching something or just grinding on its bearings. I seem to remember that there was something on this site about removing the fan possibly via the speaker hole on the dashboard. I just got used to it and remembered to get to the dial quickly. It certainly woke up any sleepy passengers though. Good luck.
garbla900
 

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I had the same problem with my interior fan. It would make a loud roaring noise if I made a turn, braked and/or on cold days.

When I replaced the fan I noticed that the bolt holding the plastic fan on the motor was lose which was causing lateral movement. You might be able to get away with just tightning the bolt back up.
 

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Discussion Starter #8
garbla900 said:
Hi

This happened on my 1990 900i as well but it only happened either when I braked very hard or when I was braking when going down a steep hill. It only stopped if I turned the vent setting to 0 i.e. the fan switched off. I never did find out what the problem was as I sold the car but I suspected that the fan itself was loose and when braking it somehow moved on its bearing and was either touching something or just grinding on its bearings. I seem to remember that there was something on this site about removing the fan possibly via the speaker hole on the dashboard. I just got used to it and remembered to get to the dial quickly. It certainly woke up any sleepy passengers though. Good luck.
garbla900
Glad to know I'm not the only one with this issue, but to get to the guts of the fan it's a dash out job I'm afraid :(
 

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Discussion Starter #9
DosEvil said:
I had the same problem with my interior fan. It would make a loud roaring noise if I made a turn, braked and/or on cold days.

When I replaced the fan I noticed that the bolt holding the plastic fan on the motor was lose which was causing lateral movement. You might be able to get away with just tightning the bolt back up.
Interesting find, did you tighten the nut and test. maybe I'll try this before I buy a new part. They are about £50 new. Thanks for the posting. :cool:
 

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You might be able to reach up through the bonnet air intake far enough to tighten that nut without having to move the dash at all.
 

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Discussion Starter #12
cdaly said:
You might be able to reach up through the bonnet air intake far enough to tighten that nut without having to move the dash at all.
Got to be worth a try, but it might require a Jeremy Beadle hand to get to it! :cheesy:
 
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