Voltage dropping after car warms up - 2.6 V6 Cabriolet

[cableguy11]

Hi Guys,
My car recently developed this issue, where after driving it for around 20mins, the battery light comes on and I can see the voltage drops to just under 12V.
When you first fire up the car, the voltage sits around 13.8V then eventually it drops and battery light comes on.

The car runs fine and i dont get any other warning lights.
Im just worried its going to drain the battery and leave me stuck somewhere.

The Car is a 1995 2.6 V6 manual with the ABC engine.

[newsh]

Pull the brushes on your alternator, they may be worn.

[cableguy11]

Thank you, brushes is what i was also thinking. I just crawled under the car, and pulled off what looks like the air scoop that cools down the Alternator. It was stuck jam with leaves. Perhaps thats causing the over heating.

Out of intrest, would anyone know how to find the correct part number for this car. Is there a reliable site?
Having looked around, it seems there are two types of Brushes.

[cableguy11]

ok I answered my own question.

This site is very useful for finding part numbers and diagrams:

https://ifinterface.com/page/page3.php?langid=1

and click on "CarProg2"

[newsh]

Sometimes the alternator has been changed.
Best to unscrew the 2 small bolts and take out the brush/ reg assembly and get the Bosch p/n

[cableguy11]

Sometimes the alternator has been changed.
Best to unscrew the 2 small bolts and take out the brush/ reg assembly and get the Bosch p/n

Is that possible with the alternator still on? There is a cover on the back of the Alternator, and i couldnt work out if it was possible to pull it off.

[Bowie69]

Had very similar symptoms recently, pulled the brush pack and replaced with a good Bosch item, this was my experience:

https://www.s2forum.com/forum/member...51#post2104651

Not sure if the V6 alternator is the same however...

[newsh]

The cover is held on with some small (not sure if M5 or M6?) nuts. Should come off.
Disconnect the batter though, you don’t want to short the main + terminal *boom*

[cableguy11]

Thanks guys

I had a go yesterday evening to try and take that cover off, and the bolts are 8mm. I only managed to take one off, there was no way of getting to the other two without taking off the Alternator.

It looks like i have to take out the alternator to get to the brushes. I think its held on by two bolts, and i just have to loosen the tensioner to release the belt.

Also my alternator looks to be a ValeoAlternator.JPG

[Bowie69]

Looks to be a different part number for the reg then, any auto electrics place should be able to fix it, or if the part number is visible when removed, just google/ebay it

[cableguy11]

Yea i think i managed to get the part numbers off that CarProg site i posted earlier. Just to double check i took the belt off and measured it.

So the belt is 6 groove V belt 1675mm long part number : 078 903 137

Alternator is a 90A Valeo with the part number 058 903 018 BX

and the regulator is made by hella, part number 078 903 803 A,

when i looked for the part using audi numbers, prices are double. Used Autodoc (the only thing its good for) to find the manufacturer number and it was £25. got it off fleabay.

Hopefully that should sort it.

[steve briance]

Ive just replaced the regulator on my cq20v and on taking the regulator out, found the brushes were probably only 4 or 5mm long and one was shorter than the other. No warning lights or trouble on the voltmetre but, using a digital multimetre to check, i now get only a 0.2v drop with load. The really surprising thing is how my idling seems to be different. Engine return to idle seems to be under much better control and i can only think the ISV wasnt getting quite the voltage it needed to work properly.

Happy days.

[newsh]