She may be old but is kept in good condition. I have sailed through the tropics on its world cruises and have found the air conditioning very effective. Don't always believe the reviews you read for there are some whose idea of a holiday is to seek faults and would complain in paradise!
Although I haven't sailed on this ship for four years I have never experienced any faults in the air conditioning system. However, it is possible that you may be confusing Fred. Olsen's Black Watch with the even older Black Prince and this does have some problems in it's air conditioning system.