Hi I have a t6 done 125000m that has developed a low pitch drone noise like a bearing going while idling, took the belt off and ran it up which made the noise go away so span all pulleys alternator etc and all seem good but when trying the ac pump it seemed to have a fair bit of drag in it but I notice these don’t have a clutch on the pulley! Do they tend to fail often or do they have a clutch inside that isn’t working? Thanks