i had exactly the same problem with my 306 meridian i was ready to
trade it in or get it scrapped had tried everything for changing both
temp sensors to auto electricians! but stumbled across the fault at
night by accident! To the left of the battery is a gap where a cable
from the neg goes and the connects else chack to make sure that the
cable is still connected as mine must have been crimped to tight and
the copper had snapped and the clicking noise was when the cables
would touch over bumps! making the dials go crazy after making the
connection have now bin fault free for a week apart from auto elecs
telling me the ECU needs replacing cos the fault wont clear! not so
keen to part with £650 like!! hope this works mate