I do not have an answer yet but will keep you informed if I find out. I have a 1999 Ford galaxy with the same problem and called in Aircon direct assuming they fixed aircon faults as their website led me to beleive that. Not true they were only a re-gassing service and I was left with a bill for £70+ just for a re-gas and was informed the problem was electrical. I checked all fuses and wiring then decided to contact another company first checking that they did repair A/C systems 2 days later the car came back with a bill for £400+ and was advised it's better only in the respect tat it runs a bit longer from cold and packs up. Great I thought does nobody in the UK know anything about aircon in cars the only thought I have at the moment is airCONNED.The last repairer said it had been re-gassed twice and that the Drier/Accumlator was replaced also Expansion unit.
So you can possibly rule these out on yours. I do have a suspicion that the problem may lie in the Evaporator wihich is part of the A/C aqnd heater unit mounted behind the dash on mine it is accessed via the removal of heater /Aicon controls fascia and removal of radio. I shall attempt to look at this but cannot be sure if I will see or find any fault. if you suspect the gas level Halfords are now selling a pressure guage to check this not sure of cost as it wasn't priced but it should be a lot cheaper than a visit from a useless re-gassing company.
Hope this info may help you avoid the cash traps that I have fallen into and should I find out what the cause is I will be the first to share this with you. Good hunting.
william.hunter1@tiscali.co.uk
August 2005