my aircon works for a few days then stops working and blows in hot air ,,, a few days later it will work perfect again

 

is there any  sensors I can replace on the unit ?

 

I brought it to a local mechanic he put it on his computer no faults showed up, I rang the local skoda dealer all they want to do is replace the compressor

 

is there any sensor or that I can replace to see if this will help. I just cant understand why it works perfect for  a few days and then wont work at all  and few days later just start working again that's why im thinking faulty sensor //?

You really need someone with a manifold gauge set or an a/c service machine (has the gauges built in) to check the high side and low side pressures. If the pressures are correct but you don't get cold air, then it could be a problem in the heater box. Just relying on fault codes often doesn't help with a/c problems.

If it was triggering the high or low pressure cutouts it would most likely log a fault code of some description. 

 

Run the A/C flat out and check to see if the fans are running under the bonnet. Also check to see if the large aluminium pipe that runs back to the compressor (under the alternator) is ice cold. Watch out for the rotating aux belt, fans and the like! 

 

It could be something as simple as a flap/damper sticking behind the dash. VCDS will be able to analyse this and determine the actual position vs the required position of the flaps, it can also carry out a test cycle of all climate control flaps. 

 

It might be worth getting someone with VCDS to hook up to it and see it that helps, the mechanic's generic scanning tool might not be able to fully check for 'soft' fault codes and the like.