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Discussion Starter · #1 ·
Hello guys!

So last week my car AC decided to work only on high speed and then never stopped when i took the key out... i did not realise since my cooling or something still works after i turn of the car for some seconds... a lot of noises actually... the next morning car was dead and as soon as i jump started it the fan kept going... i saw on the forum info about the FSU so i ordered a new one, but since i m a student and i did not have money i bought one for cheap from a junk yard. Now the weird part begins.

When i changed the FSU i noticed that the one that was in my car was some after market unit and the junk yard one was original BMW (the one with fewer and bigger spikes). The problem was somehow solved, now the fan shuts down with the car but it will only work on one speed (kind of medium)... the +/- dial was not working and also the max snowflake was not working... i figured the "new" FSU was also broken, but les broken than the last one so ill be able to live with just half speed.

Then the next day i turn the car on and nothing... silence... i could hear the flaps that direct the air moving when i clange from feet to middle and windshield, but nothing else and warm air was coming out bot not blowed... just easing through... i used the car like that for 1 day but it was super bad since it took ages to defog...

Then the third day i said that's it i'm going to a mechanic and as i entered the car the fan started to work and not only that, but now i had speeds too... the +/- was working again just fine... but i did notice a "crrrr" rattle that i have never heard before... like a wire or something is touching the fan as it spins... apart from that it workes just fine for 2 days... and now this evening i went to the gym, it worked and when i left silence again... as i got home i played with the HVAC buttons and again i hear everything working apart from the fan... there is a sound starting when i start the AC but i don't know how to desctibe it... like a faint airplane noise from the center colsole... i guess that is the blower motor... and i also hear for like half a second the "crrr" sound just when the AC starts and then silence... so wild guess would be that it's not a bad FSU, but something touching the fan and preventing it from working?... or is ot both... i really don't want to buy a second FSU.... does anyone know why is this?

Sorry for the bad english and thanks a lot for reading
The car is a 2001 e39 sedan
 

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The faint whirring sound may be the sampling fan. The left vent on you ihke is a sampler to detect your cabin temp.

Does your vehicle go to “sleep”?

It at be a ad FSR or it could be poor circuit connection...


2001 750iL DD74441
E65 fan & clutch, E65 headrests, Front First Aid Kit, Ultimate Cup holder

2005 X5 4.8is LE82680
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RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1
 

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Did you have the system tested for refrigerant?
Looking at your HVAC you see small ventilation holes on the left and right, inside the right vent is a temperature sensor, behind that is a little fan and it can make like a ticking noise. Try using the vacuum cleaner on the vents, it might help. If not, take out the MID, put your hand down and push the hvac unit out, disconnect all cables.
Carefully loosen all the plastic retainers and slide the cover off, now you see the little fan on the circuit board, lift it off, clean the spindle, the fan and around the temperature sensor, put everything together again.
Your car will go to sleep 16 minutes after you leave it alone.
 

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Discussion Starter · #5 ·
I pulled our an cleaned all the connections on the HVAC and the little fan... it's definetly the AC fan that does that sound and all of it works ok all the buttons and everyrhing... like i said in one of those 3 days it suddenly started and everything worked perfect appart from that "crrr" sound... i only heard it while the AC fan was running and the little fan in the HVAC runs even if the main AC doesn't.... for the sleep part I don't know how to test... i know that you still have electricity running for a while in the car after pulling the key to shut windows and sunroof and stuff and after a while they all stop working, but that's all i know... i guess the car shoul die till morning if not ?
 

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Like I said, the car goes to sleep after 16 minutes, if you have a little orange dot light up next to the gear lever it will go out after 16 minutes, or you can open the trunk and after 16 minutes the light will go out.
 

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Discussion Starter · #8 ·
I know somebody with an e39 that has a new FSU installed and i asked him if i can put it on my car tomorrow, and if it works i will buy another one, but my fear is that the fan is hitting something or it's broken, and i know that's not really a DIY job... and if it is hitting something and it's some sort of wire i don't want the car to catch on fire... i say that cause at my PC sometimes the cooling fan wire rests on the cooling fan itself and it makes the exact same sound
 

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Did you have the system tested for refrigerant?
Looking at your HVAC you see small ventilation holes on the left and right, inside the right vent is a temperature sensor, behind that is a little fan and it can make like a ticking noise. Try using the vacuum cleaner on the vents, it might help. If not, take out the MID, put your hand down and push the hvac unit out, disconnect all cables.
Carefully loosen all the plastic retainers and slide the cover off, now you see the little fan on the circuit board, lift it off, clean the spindle, the fan and around the temperature sensor, put everything together again.
Your car will go to sleep 16 minutes after you leave it alone.
Huh, so maybe all European E39 models have the sampling fan on the right side of the HVAC control panel no matter if they are left hand drive or right hand drive.
I know all U.S. models have the fan on the left side of the HVAC panel and the little vent on the passenger (right hand side) is a dummy/faux vent.
I can see that yours is on the right hand side of the HVAC panel because I can see the light reflection on that little clear, square piece of plastic that is inserted at the corner of that sampling vent from the picture of your interior.
 

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It looks like your fan is out. It needs the big current to run like it is siezed. And the sound when turning on the ac without the fan running is the ac switch that controls the gas to the evaporator, you cannot hear it with the fan running.
 
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