E39 Aircon problem

[liyi_92 37]

Car is a 1998 540i. Air con seems to be stuck on max settings as soon as I turn it on.

Seems to be able to blow hot and cool air fine.

As soon as A/c turned on there is a loud humming noise coming from back of engine. Also seems to be shaking a bit from where sound is coming from too.

Any suggestions?

Thanks,

Andy

[JaseNZ 53]

I would hazard a guess the FSU (Final stage unit) is stuffed.

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Edited September 17, 2012 by M-Spec

[liyi_92 37]

Should I just buy the part and DIY or worth it to take to Kevin Burt to see whats wrong and fix it which will probably cost a small fortune

[JaseNZ 53]

Should I just buy the part and DIY or worth it to take to Kevin Burt to see whats wrong and fix it which will probably cost a small fortune

That is the million dollar question lol, It being stuck on full points to a stuffed fsu but does not explain the noise you are hearing unless its the noise of it being on full and you are not used to hearing it. Perhaps go to the wrecker and ask if you could swap out your fsu to test if its it and if it is get a new one do not get a cheap one off of ebay get oem

Edited September 17, 2012 by M-Spec

[liyi_92 37]

Are the FSU or blower motor resistor used compatible between models and years? So would a 528i FSU work on my 540i etc? Thanks

[kiwi535 538]

Are the FSU or blower motor resistor used compatible between models and years? So would a 528i FSU work on my 540i etc? Thanks

why dont you just get a diagnoses to see what the problem actually is and go from there,no repairs just a report whats wrong