Battery light V6 GTV

[Rewe 8]

Can anyone shed some light on an interesting issue I've had with my daily driver V6 GTV over the last four years? Most mornings the battery light goes straight out, but sometimes it will take two or three minutes to extinguish. When it goes out the odometer gets noticeably brighter so I think that it genuinely does take a while for the alternator to wake up (unless the problem only exists in the instrument cluster).

 

Clues:

 

It only does it in the mornings, never after work in the evening.

It is more likely to do it when it is cold, but it occurs randomly

If I have covered a decent mileage the day before (>100 miles)it is more likely to do it the next day, regardless of the weather.

The battery is excellent - it spins the engine like a good'un which fires almost instantly. It did not do it any more or any less with the older, tired battery.

It has not become any worse nor any better over the last four years

Putting all the electrics on or all off seems to make no difference to how quickly it goes out. Nor does increasing the revs.

I've had a couple of half-hearted attempts to check the battery voltage on start up, but have never been quick enough to catch it with the light on (and now I've broken my multimeter )

 

I've learnt to just live with it and not worry but I'd love to know what the root cause is.

 

P.S. Smaky, just in case this is heading where I think it is, what are the chances of a alternator replacement guide.

[Anjenha 44]

Stupid, I know, but could it be a dickie switch?

 

My passenger airbag on the old Spider could never decide if it was on or off. If I put the key in and wiggled it, it would then read the correct position ( be that on or off )

 

 

Just a suggestion

[ChrisO 2]

If the battery light is on then it normally means that the alternator is not charging (hence the dim lights). This could be down to serveral different issues i.e. is the alt belt slipping, a loose cable etc etc etc - it sounds like it is charging so it is probably something minor not a major alternator replace.

[Smaky 73]

I've seen this on a couple of 916 GTVs and Spiders, it is down to a contaminated/dry joint inside the cluster, they seem to be prone to allowing moisture in as the cool through the night and this drys out and slowly corrodes the plug terminals inside, as the volage detection circuit is inside there then I would suggest opening up the cluster and claening off the umbilicle with some IPA spray and a gentle dusting.

[Rewe 8]

A free repair I can do myself!

 

I've never taken the cluster off, let alone opened it up. Will it be obvious, or is there anything I need to look out for?

[Smaky 73]

A free repair I can do myself!

 

I've never taken the cluster off, let alone opened it up. Will it be obvious, or is there anything I need to look out for?

 

It will be obious as a large white furring stain on the 'board', worst case is it will need replacing to solve this but if you can live with it then it's not going to cause the car to die.

[Rewe 8]

Ah thanks. What I meant to say was how hard is it to get the cluster apart? Carefully remove the two allen head bolts and set to with a big pry bar?

 

Just to be clear, when the light is on the alternator is likely to be charging but it just looks like it isn't?

[Smaky 73]

Ah thanks. What I meant to say was how hard is it to get the cluster apart? Carefully remove the two allen head bolts and set to with a big pry bar?

 

Just to be clear, when the light is on the alternator is likely to be charging but it just looks like it isn't?

 

It is just that to get itt out.

 

 

To prove it's charging when the light is on just check the voltage accross the battery, anything over 13V and I would say the alternator is working and the problem is definately in the speedo head.