Have a look for yourself. Not hard to spot what Al described. Not sure if this is a freak circumstance, but, the single fan on my van will not spin up for ages with my air con on - unless it is a very warm day - like what we have at the moment. Even then it will have to be sitting in traffic for a while until it comes to life. Still, the A/C works so well! Absolutely freezing cold most of the time (around 5-6 Celsius on the meter). If the system is decently pressurised, and holding that pressure as you say, then you are half way there... IS the compressor clicking in and out while the van is sitting @ idle with the A/C on? When i first bought my van, the main hose from the alloy union joint was completely split open. £250 later
(ford only part!) It has been working faultlessly for about 5 years without a re-gas, just as systems should - provided there is no leak! Good luck with this mate. All the best