berlingo 2.0 hdi 2005 - noise from engine bay when engine off?

berlingo 2.0 hdi 2005.

i heard a whining noise that sounded like a motor running after switching off the engine.

this continued for some time so i disconnected the battery - the noise continued and then slowly, slowly, slowly, the noise subsided almost like a motor winding down - took about 5 minutes.

after this i started engine then stopped engine. noise occured again - appears to be below battery area, above clutch housing.

after about 30 seconds, the ecu [or a relay in same area] clicked and the tone of the noise changed - like the speed of a motor changing.

disconnecting battery had no effect!!

anyone please advise what this is?

thanks.