"Brake light failure" is either one one of two things - a failed bulb
or a socket assembly that is on the blink (no pun intended). What
happens is that the two little contacts on the sides of the bulb
socket get oxidized and thus start losing contact. The first time I
figured this out, I scraped them with a knife and the socket started
working again. Then I ordered a couple of spare sockets. The 2nd time
it happened (about 6 months later) I simply replaced the socket. This
has happened on my '96 328i and my wife's '94 325i.
"Brake light circuit failure" refers probably to the brake light
switch, located just behind the brake pedal. This switch fails after
100,000 miles, give or take 10K. When this happened to me on my '96, I
ordered the "mechanical" switch replacement part from an online
distributor for about $20. Putting it in was a little bit challenging,
mostly from laying on my back with my head under the dash, etc. When
it failed again after about a year, I ordered the "electronic" version
of the switch for about $27. That was about 3 months ago, so I don't
know about the long-term viability. I have a feeling that the
electronic version will last a lot longer and I think it was what was
originally in the car and lasted nearly 10 years.
The fan in your AC unit going on the blink is related to a capacitor
(electronic component) that fails. I was able to find a web site that
described how to disassemble your AC control unit, pull out the
circuit board and replace this component. I followed the instructions
and mine has worked perfectly since then (about a year ago).
Hope this helps!