Battery drain connect charger after a minute or so there is a whirring noise from under the bonnet voltage jumps from 6 volts to 13 anyone have any ideas why ?

Morning William 

Welcome to the Forum

First how old is your battery ? What is it's condition ? If your getting a "whirring noise" you need to see what it is that's running Cooling Fan ? Recirculation Fan ? Emissions Fan ? Fuel Pump ? Is the key in the ignition (it shouldn't be) If you have a system that is damaged and running try pulling the fuse obviously what ever it is it needs repair/replacement 

If Battery voltage is bellow 12 volts at rest "engine off" it is probably dead and needs replacing, when charging you should be connecting the charge at the charge points under the bonnet. A fully charged battery should be 12.8volts engine off, around 14.5+ volts engine running. 

Dave

 

Hi battery is 3 months old  just went to start car, battery flat even though it started and ran 15 minutes ago. I put multi meter on with key out of the ignition voltage was jumping all over the place, what would make the voltage unstable?

Hi

Where are you measuring the voltage? 

Your car has around 25 control modules all of which communicate with each other over the Bus system so with out diagnostics very hard to tell. though you could pull fuses until you find the culprit. But not necessarily the cause

When the new battery was fitted was it fitted correctly? is it the correct battery and type for the car? was it correctly registered to the chassis ?

If the battery is not correct, does your car gave stop/start, then it quite possibly is dead, if it isnt registered to the chassis it wont charge correctly.

Dave

Measuring under bonnet replaced battery with the same. Have now tried another battery, will check in the morning cheers