The Red battery light of Joy
 

Driving the S8 this evening and having a great drive in a wonderful car.

On the way home the red battery light came on that is on the rev counter. Most odd I thought as the car is going well and its got a new battery in the back.

Stayed on and I was thinking hello is this an Alternator problem....

Driving through Cheltenham and more warning lights came on, dash dimming, battery light on the DIS, gearbox goes into limp and yes the poor old battery was clearly being drained and not charged. Luckily got it just to a friends house and parked it up and I can worry about it tomorrow. So its either going to be an alternator failing (was working fine) or its thrown the belt due to a grumpy tensioner.

I mean I cannot be too hard on the old girl it is 18 years old and done over 200k so the occasional old part is allowed to wear out!

First thing I'd check is the battery terminals to ensure they are fitted securely, and you don't even get your hands dirty.

Next would be a visible inspection of the connection block on the front drivers side chassis leg to see if there's a buildup of crud.

Failing that, await an answer from MJ :)

Beg, borrow, perhaps not steal a multimeter from someone, put it on volts and put the leads across the battery terminals. Start the car and check what voltage your alternator is putting out. Quick and easy test. Should be about 14.4V. If it's low, and I suspect it will be, I'd then repeat the test at the terminal box in the wheel arch but place the meter leads between the big battery cable and the chassis. You will have to probe around a bit on the battery cables because it is possible that a bad terminal box connection will give a poor result on the long cable going back to the battery and a good result on the shorter cable. This would actually be a good thing as it would indicate a bad connection in the box. An easy ish fix.

If all is well here then you need to be checking out the alternator. Could be poor connection's there or brushes worn-out.

Brushes are easy to replace, no soldering required but I am unsure if it can be done with the alternator on the car. Not sure if there is enough room to remove the rear cover and air duct to get access.

Thanks for that, yes have a multimeter as tested it a while back when I had a Yuasa Silver battery causing no end of problems.

Got the car back home tonight which is good news.

Put a spare battery in and started OK, still had the red battery light on the dash. Then the car was running rough and really rich, then it died...

.....and would not start again even after a period of time to see if was flooded :(

Called the RAC and said they would be about three hours!!!!!!!

This would normally be the end of the story but I disconnected everything, let is reset and then forced the car to start on LPG. Drove home no problems (red battery light still on of course).

Ahhh all in the pouring rain also.

Never mind, Hooray for LPG +++

You may have killed the fuel pump running it low on volts. I've seen that before when the alternator has died and the car was driven until the battery went flat.

The alternator does need to come off to replace the regulator so at that point its as easy to just fit a recon, although if you can afford to have the car offline for a few days a regulator is a cheap enough to try. If you buy a recon, make sure its for a V8, not a V6. A lot of places say they are the same, but the rear air ducting is different. The V6 alternator will bolt up but the ducting then won't fit.

It can be on the drive/ in the garage for a while so I agree I will take the alternator off and try a regulator first of all.

Then look at the fueling, it could well be the pump has decided to die at the same time just to help matters! I will give it a tickle with VAGCOM to see if it throws any light on the matter.

Does anyone have the part number for an S8 Regulator?

028903803e

Thank you +++

Nognar - I still have a V8 alternator [Bosch] rated at 150 amps sitting in my hallway. A replacement was obtained from Prestige and was fitted to my car after experiencing charging problems with, you've guessed it, a silver Yuasa battery. I'm convinced it was working before I foolishly replaced it but haven't tested it.

If it can be of any use, let me know either in this forum thread or a private message. The only possible caveat being that the S8 alternator is different to an A8?

V8 alternators are all the same +++