1999 Pug 406 110 Hdi - Drive belt tension problems

[VespaSkin]

Think it's the alternator or pas - scrappy got a p reg and a r reg in, will these 2 bits be transferrable? they charge a £10 each so might get them just to try out

[VespaSkin]

Back again...

2 questions....

1.) would a knackered air con pump cause a battery fault light
2.) any ideas what length belt you'd need if I take air con pump off?, the original was 1745mm or something, local factor sold me one that was for 406 non aircon and was wayyyyyyyy too short

Cheers

Gaz