Hello Beany,
Thanks for the important additional information - it would have saved two of us suggesting what you have already done!
Alternator output at 14.1v is lower than expected, and at 13.7v ,is unacceptable. If all connections and earth leads are sound and serviceable, then it suggests you have an alternator issue and the clicking is likely to be an associated symptom.
Kind regards,
Gareth.