Batttery power...

[logeyboy]

Last week I suffered a complete flat battery when trying to re-start at the petrol station 

I put the battery on charge for 24 hours and it's been starting ok(ish) all week but still doesn't seem to be fully charged.
This morning I was happily driving along when I put the rear de-mist on. This made my stereo turn off? I turned the de-mist off and the stereo came back on.

It seemed to me like a power issue? If so do you think it's the battery (about 5 years old I'm told) or could it be the alternator?

If it's the alternator, I've seen 2 different ones. A 65amp & 90amp.
Which would I need for my 1989 Mk2 8V GTi???

Thanks guys.

(anyone prepared to give me a jump start after work?)

[JC]

multimeter time

battery should be 12v with the engine off - 14v with the engine running across the terminals.

then go from there 

[wriggley]

if battery was completley flat it could be that the cells in the battery are damaged and wont hold there charge properley ive had this problem and a new battery cured it 5 years old aswell wouldnt hurt to change it realy any way as to the alternator i dont know i would also like this info for a 16v which amp is it lol

[daniel-1986]

If it's the alternator, I've seen 2 different ones. A 65amp & 90amp.
Which would I need for my 1989 Mk2 8V GTi???

i should have a sticker on the alternator saying the manufacturor and what amp it is