Alternator problem

I have just replaced the standard alternator on my 300 Defender with a 100 amp one and was wondering if I need to replace the wiring, when trying to start the engine am only getting a clicking noise. Tested the battery but its flat and was only charged yesterday. HELP! The starter had been playing up and think may have to replace this as well

was you making up for a poor battery with a new alt ,how have you wired alt battery live to B+ ignition wire d+ rev counter wire w

Wired as per original one, will double check. Battery may be the cause but thought it was alternator, thanks

terminals are marked it worth checking

Assuming of course the new alternator is new and hasn't got a faulty diode pack.