I have a 1985 528E and need to fix the A/C.
Question 1:
 I bought a reconditioned Bosch air compressor from the parts house and it has a wire coming off it behind the clutch. Do I splice this onto the existing item on the old compressor and then mount that item on the new compressor?
I take it that the item in question is a diode? It is a small black square item with a wire on each side. The second wire goes to the compressor clutch backside.

Question 2:
 I also bought a new drier. How much of an oil charge (R12) do I put into the drier?

Question 3:
 I bought a new expansion valve and have absolutely no idea of where this expansion valve can be found.

 Hoping someone can give me some help on this problem. Thanks in advance........ pg