BMW Repair: E21/320i belts, reddish fluid, auto parts stores

Question
I have a 1983 320i with a 1.8L engine. I have the standard V-belt that drives the alternator and water pump. Lo and behold, there is another belt that's missing. It doesn't show up on any of the diagrams or manuals I've found. It would run through the flywheel and over to a "box" on the left as you stand in front. The box is leaking reddish fluid, like power steering. However, there is no fill point. I assume (right or wrong) that the bos is leaking, because the belt is missing and the fluid is not being pumped. So, what is the box? I hope once I can figure that out, I can find a belt and new seals.
Thanks.

Answer
The "box" is I believe your A/C compressor,the reason for no belt is it must be leaking.You had mentioned some liquid? coming from it ,well that probably is a/c oil with a dye in, to find the leak.To fing it now you will have to clean the area and start with pulling a vaccum to see if it will hold,if it does than you can start to recharge.R12 is not available easily now so the system will have to be converted to R134,which can be purchased at all auto parts stores.