Im surprised that your freon checks out because the 140 chassis usually has a problem with the evaporator leaking. Well what isnt the ac doing ie engaging the compressor clutch. IF that is the case i would check that the clutch is getting power when you engage the ac system. If it is not which is probably the case work your way up the system. I would also chech the etr if that is telling the ac system that the evaporator is too cold then it wont turn the ac compressor on either. There is a way to go into self diagnosis with the acc but i forgot because at the dealer we would just use the hht. Sorry for not being more specific.
1982 300D Turbo (Mom's)
1993 BMW 525I (Dad's)
2001 Vw Golf (Brothers)
2002 Nissan Ser SpecV (Im the Black sheep lol)