Fitting AC on car that didn't come with it?
 

I have a 96 s40 without AC fitted.
Is it possible to take all the parts from a car that did come with AC and fit them to my car and end up with working air con?

Provided you get all the parts needed there's no logical reason why not.

Well, i found a 96 v40 with AC and mecanichally everything would fit. It has been sitting as parts for around 1 year but the owner remembers the AC used to work. Would the seals and Orings still be good or would they be easy to buy new?
Do I need to change something with the ecu or electronics of my car provided it didn't have AC fitted?

you would need to change the heater controls unless yours are the same , and the AC is controlled by the engine ECU so who knows whether you need a new loom , I'm sure there will be unforeseen difficulties with your plan..

"... It has been sitting as parts for around 1 year but the owner remembers the AC used to work. "

Not the best starting position for an air-con system that you're going to unbolt, remove and then install in your car.

As has been said already, " ... I forsee unforseen problems, minister."

Does anyone have a wiring diagram for AC system?
I took out all the AC parts and everything fits mechanically. All i need to do now is wire the compressor.