meracus

thanks for all the reply
I'm taking the car to the workshop next week
its been really helpful to get an insight into what could possibly be wrong, I could lay it bare to the technician ( I'm sure he will take it well knowing I gleaned it from a forum )
but at least, I'll ask him to thoroughly check every one of these points

billwot

I hope I don't sound argumentative, but it isn't about the"same drop". If there is any residual moisture entrained in the system, it will freeze at the expansion valve, and interrupt the flow of refrigerant. And it's really a pretty simple diagnostic with a set of gauges. If the hi side goes way up, and the low side goes below the low side cut off, then its pretty obvious the system is blocked. And if its an intermittent condition (which is my understanding) , then its pretty likely there is moisture at the expansion valve. (freezes and melts)

And your correct, it obviously is NOT a leak. And regardless of the specifics, the problem very probably is at the expansion valve.

But, without some pressure readings, its all just conjecture. Any competetent tech could make a reasonable diagnosis pretty quickly with a set of refrigeration gauges.