While rooting about in the engine bay as you do, I noticed that the air intake for the alternator fan seemed a little loose.
Closer investigation revealed that the fan housing had split in two and the feeder hose to the alternator was no longer connected .

This air feed is needed to keep the alternator cool, as tucked away at the back of the engine as it is it will overheat and eventually expire.
Rather than just pop the top of the housing back on I figured there had to be a reason for it coming loose in the first place so I decided to investigate further and also check on the condition of the fan .
Pulling the intake and top housing out of the way reveals the fan body,


At this point I can check that the fan moves freely, it doesn