WHERE IS THE BATTERY IN a 94 x5 - 2000 BMW 3 Series

not sure on X5 but on 5 series it meant -
U112B - No message from instrument cluster, could instrument cluster fuse. Could try disconnecting and reconnecting battery to see if that clears it. (Make sure you have radio code before disconnecting)

same problem! you ever fix this?

I am having the same problem with my 2002 X5. There is a motor or fan running behind the AC control panel on the dash and if I pull fuse 48 it stops and the battery doesn't drain. Still looking for the cause and solution so that I don't have to keep pulling and installin fuse 48. BMW garage suggested that it was the Final Stage Blower Resistor. I replaced this and no change. I hope someone has an answer that will help us both.

You have likely lost programming, the dealer must reprogram the system for you with a special scanner.

Is the battery and the battery connection in good conditions? Try to charge the battery overnight with a battery charger. If then it starts your engine, the battery may be ok.
I recently had an issue with my car that the connection to the battery was corroded that was not visible just by looking at the battery. The connection had to be cleaned and solved the issue.
If the battery and generator in your vehicle is ok, then it must be a short circuit in the car that drains the battery. Locating that may require shop visit.

in rear, under spare tire

Use a portable jumper battery or a battery charger
connected in front at the jumper terminal 12+ and a
good ground .

had flat battery got it going but now got no central locking or wipers

You need to check for any lighting left on overnight if not try to fully recharge your battery and perform a load test on it to see if it will hold the charge if so possible drainage off of interior lighting switches or alarm possible

clicking is always low battery. takes heavy amps to start car. you need a battery replaced