<E34> Growling Sound when applying brakes whenever AC is on

["Nelson, Mark J" <Mark.Nelson@xxxxxxxxxxxxxx>]

I'm perplexed, please help if you can:

My 89 535i makes a growling sound while braking with the air conditioner
switched-on.  The noise seems to come from the front.  Everything is fine
with AC-off and the brakes stop well in either case.  This condition is 100%
repeatable, and never happens with the AC-off.

FYI:
- - I just purchased the car and didn't catch this problem (nor did my 
   inspection shop)
- - The AC system was recently converted to R-134 by the same shop 
- - The AC clutch seems to engage properly (I can hear it)
- - The AC belt was recently replaced and feels tight.
- - Vent air is not very cold (50 deg F) with AC-on (something's wrong?)
- - Auxiliary fan works properly
- - The upper and lower control arms were replaced recently

Thank you in advance for any help.

Mark Nelson
Seattle, WA
BMW CCA & ACA
89 535i 130,000 mi

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