I have had a new splitload CU fitted and one of the circuits on an RCD side goes to my garage,- the fuse has not tripped- which is some 20metres from the house. this is fed by a armoured cable. it is earthed from where it leaves the CU unit by the armoured wires on the cable. it is alse earthed from where the supply enters the garage again by the armoured wires, from their it feeds the various sockets and lights. But if a socket tester is pluged in then the 'earth light' on the tester does not come on. The cable has been in situ for about 15 years, and is in good condition. It would be possible to install an earthing rod in the garage location, or should that not be done.
Thanks for any advice