Airco condensor

[Dutch]

I took my car to the workshop to have the airco diagnosed and they told me the condensor was knackered. When I asked how they knew they said because the airco system is empty. Just that... nothing else... no vacuum test or presure test was done.
Having read the pressure in lexia in feb and just a couple days ago I was quite surprised as the pressures were 2.5 and even 2.6 bar a couple days ago! After they heard that, they theorised that a bit of liquid left in the system can keep it up to somewhat of a low pressure for a very long time.
So my questions are: 
How can you test yourself if any AC part is leaking/ whether the system is still closed after 10 yrs
Is the condensor a fragile part on a partner/ berlingo that often provides problems?
Or are the guys at the workshop simply correct in their diagnosis

[ffrenchie]

They can put leak detector fluid in with the refill and you will be able to see if it is leaking under a UV light.