New Battery

[minid0m]

I tried to start my mk2 8v gti today and the battery was completely flat, I then jump started it, drove about 15 miles and turned it off and wouldn't restart.

If i need a new battery where should i get one from?

[rubjonny]

Take it to Halfords they'll test it for free.  Their batteries are good quality ones rebranded too apparently.  Check the voltage across the terminals when the engine is running it should be 13-14.5v, if not the alternator isn't charging for some reason!

[minid0m]

went to halfords got a heavy duty one as the original was dead.  will have to test the alternator another time, perhaps tommorow as I don't want to f**k up the new battery... It cost £55 ouch! I sometimes wish I still had my mini...

[Gambit]

if the alternator aint chargin properly then the red light will constantly show on the dash

[rubjonny]

Will it still light up if the blue wire to the alternator is disconnected?  I was under the impression that it didn't but I might be wrong.

[diagnosis-dub]

The blue wire from the alternator makes the dash light go out as it is positively charged when the engine is running.

[minid0m]

Went back to halfords and got them to test the alternator, which turned out to be fine, except was found to be charging a little less then it should with all the tunes turned up! No problems though

[diagnosis-dub]

On most bosch alternators you can just replace the brush/regulator unit on the back for a new one and this solves the charging problems.