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.

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1982 300D Turbo (Mom's)
1993 BMW 525I (Dad's)
2001 Vw Golf (Brothers)
2002 Nissan Ser SpecV (Im the Black sheep lol)