Terrible thumping noise when either heating or cooling used.noise stops immediately when climate control switched off.car has covered 130000 miles,65000 by myself.i have very rarely used the air conditioning as it is not really necessary for nrthern irish summers.the a/c pump has been taken off and visually inspected by an independent expert who said it was not in the worst condition he had seen and give it another try.i have since discovered by selecting the economy button on the climate control system that i can get heating without the terrible racket.any idea why?