I have an aircon. compressor which was removed from my 405 SRDT when we were 1000k's from home and the spine chilling noise that occurred when the air con was turned on was diagnosed as a faulty bearing in the compressor - after replacing the compressor ($800), it was eventually determined that the bush in one of the cooling fans (which cut in when the A/C is turned on) was the real culprit! Will let go for $100 plus freight.