my carlsberg draughtmaster has stopped working?

my carlsberg draughtmaster has stopped working after only being used 3 times. unfortunately for me it is a year and a half old. the problem is that the pump does not switch off after 2 minutes when you install a new keg. I have brought more kegs from carlsberg but the same thing happens. The pump does sound louder than normal though. Any ideas anyone? it's driving me nuts having all these kegs and no way of drinking them!!!!!!!!!!!!