Hi thanks all for your reply,
I monitered the tempreture and when I switched the ac at idle I am getting 19-20 degrees C and when I drive the car I am getting around 16 degrees C at the vents.
When I switched off the ac I am getting around 24 Degrees C.Here in Malta we have very hot summer sometimes it goes to 41.

To be honest I don't know where is this mono valve or how I can check it.

Some thing strange is that the front fan is working, the sucktion line is very cold but I am not getting cold at the vents.I think that the compressor is doing it's job because the gauges are reading 40 low and 250 at the high side.

I put 8oz ester oil in the system which I read it's good for both r12 and r134a.

When I have the ac switched off the readings are totally different the low side is very high and the high side is low,is this something wrong with the compressor?

Thanks all for your time and helpfull information.