Starter motor or battery? or something else?

Hi all, got a starting issue (1,3 mk1 citi golf)

Sometimes when starting the starter motor goes really slow then clicks, tested the battery and it shows 12.4V, so i thought this should be enough to start her, when i get a jump start from another car she fires up fine, so is it an issue with the starter motor or is the battery dodgy and giving out a false reading or breaking down when starting?

btw, all connections are clean and it's a new alternator.

Thanks for any help, need to sort this today and i need to get the right part

Many thanks

New battery needed  


Just because it reads over 12volt is no indication as to the condition . You should have over 14 volts when engine running at the battery terminals , with out a special tester you can't tell how a battery is performing


?30.00 should see a decent one purchased…

Cheers………..

Thanks, i'll get one in the morning