A/C stopped working...
 

My wife's 1991 525i (193,000 mi) was blowing very cold last time I checked it (about 4 weeks ago -- I live in Florida). My wife mentioned to me today the A/C is not blowing cold. I noticed when the A/C button is enganged, the light does not turn-on (button light) and the compressor does not turn on. All fuses (#9, 20, 27, and 29) are all good. Where do I go next? Is there a relay for the A/C?

According to Bentley section 610-1 Fuses and Relays, there is a relay for the compressor. The relay is located in the Front power distribution box (driver side on US model next to the strut tower). It is located on the third row, starting with the row of fuses, then the second row of relays(orange color) should be 3 each if no factory phone, 4 if with factory phone, the next row are smaller relays (black color), from left to right if you're standing on the driver side. The first black relay (about an inch square) is the compressor relay, part #61.36-1 393 412(on my 92 525ia). Actually there is four of these relay, one next to the compresser relay is for the Washer pump, the other two on the right side is for the Aux water pump, and Horn relay. Swap one of these relay with the compressor relay and see if the AC works, for example swap the Horn relay with the compressor relay to see if the AC or the horn works. Hope this help.

glen-sj