The AC problems could be the belt being too loose or the AC compressor locked up. Either way it needs attention from a tech that knows Mercedes. You will have to describe the button a little better for me to tell you which one you are speaking of... as for tips we will get them when we start selling parts and other assorted goodies to the customers of MercedesShop! Thanks for your support!
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM