intermittent flat battery

[stevej 0]

hi,

 

keep getting above problem. starts fine on jump leads & runs fine once started. my initial susipcion was battery not holding charge as opposed to alternator prob. howver both have been checked and are apparently normal. i still eckon it may be the battery ??

 

Any thoughts appreciated

[Supercharged 2]

First off take your parcel shelf out and check the boot lights not staying on... a common fault

 

If not You need to do a drop test... basically measure current drawn with the engine off, anything over 0.1 amp shows a fault, you then need to pull fuses one at a time until that figure goes to normal (closer to zero) - once you know what circuit the faults on you can start looking at individual components..

[Riley 0]

This may help

 

Neil.

[stevej 0]

thanks for that info guys, its appreciated.

[Mystic Rado 0]

It might just be the battery - I had a similar problem, but the battery seemed to be holding charge, car just wouldn't start if it wasn't used for a day or so, I put it down to the alarm draining the battery and bought one of those solar panel charger things.

 

Anyway, to cut a long story short, car started, got from Manchester way down to Newport Pagnell then refused to start after I'd filled the tank up. Called the AA cos i was worried it was a charging problem, he did some tests, said the alternator etc were fine, but the battery, although it was holding charge and giving a reasonable reading, simply didn't have the ooomph to turn the motor over. Apparently they can do that, it's something like being able to run slowly round a track for 1500 metres, but not being able to do a sprint start, or that's how I interpreted it anyway...

 

Bought a new battery from Halfords once I got down to London, stuck it in and it's been spot on ever since, I leave the solar trickle charger on as it's used mostly at weekends.

 

So, if the battery's oldish and particularly if it's discharged completely a few times, it might be the problem, even though it might seem to be okay. If, after checking, you can't find anything else amiss, a new battery might be the answer.

[dr_mat 0]

...the battery, although it was holding charge and giving a reasonable reading, simply didn't have the ooomph to turn the motor over. Apparently they can do that, it's something like being able to run slowly round a track for 1500 metres, but not being able to do a sprint start, or that's how I interpreted it anyway...

 

Yep, the plates in the cells get coated in sulphates, which prevents them from conducting electricity. The much reduced surface area available to conduct electricity means that you still see 12V output, but the battery can't pass the 100+ AMPS required to turn the start over.

 

So, if the battery's oldish and particularly if it's discharged completely a few times..

 

Indeed - it's when the battery is low on charge that sulphates start to build up.

 

They can test this at the tyre/battery places. They have a big-arse wire with a meter on it that puts a short across the battery and measure how much current it can dump through the wire. If it's pushing lots of current, you have a healthy battery that just needs a recharge.

[Jim 2]

Has it suddenly become more of a problem now the weather has gotten colder? I remember on my first Corrado leaving the headlights on a few times and flattening the battery and it seemed to knacker it to the point that when it got round to autumn / winter, the heavy use of electrics whenever I drove (heater, etc) combined with really cold nights meant the battery just could not cope.

 

Picked up a nice, bigger capacity Bosch Silver and it was fine ever since :)

[stevej 0]

no battery drain.

 

fitted new battery. seems ok but for how long ???

 

the whoe thing was pretty similar to what had experienced.

 

thanks.

[achaleven 0]

Local VW agent told me this has been a problem with the VR6, well, for ever. Something to do with the engine computer not going to 'sleep' when it should! I took his advice and invested £10 on a solar panel. I leave it for 4 weeks at a time now and it starts 1st time, no probs.