Romanrob

Thanks. The battery was a Varta, most likely Audi issue, as it has a BEM code on it, and was coded into VCDS. I cant be 100pc sure that its 7yo as we have only had it 5, but its pretty likely. I now have a brand new identical Bosch S5, replacing a properly programmed VAG battery so no issues ( i advanced the battery serial number by one digit, so the car knows it's a new battery) The alternator warning was semi-permanently on saying alternator not charging, usually triggered by the use of high demand equipment (aircon or Headlights). VCDS said electrical problem with generator, and reported an energy management shut down of the aircon etc. Physically, when I removed the VR the brushes and slip rings were majorly worn. In addition a load test with lights and air con was only kicking out about 11v from the alternator. After a recent long journey the battery was off from 12.8v to 11v, and draining the battery at 25 A. Could I rebuild the alternator etc? Maybe, but its the wife's car, and i have a day job, so I'm just buying a replacement and putting it in. The point being, if you do it yourself you save stacks on Audi labour, so can afford to bolt on a new one.

The alternator kicks out 140A max, and the battery is charged at 7A or so, so I dont think your choice of battery has much of an impact on the alternator, but again, you need the energy managent system programmed right...

Hi Magnet, batteries not my area of expertise either... My battery wasnt AGM, so I didn't encounter this issue, but if you have stop start on your car, I don't, then i wouldnt switch types as the demands on the battery is completely different. If you do switch you'd defo have to reprogram the new type and for that you need VCDS too

Niedzal, maybe, maybe not... The coding relates to badged capacity, ageing, and a learned charge state. I'm pretty sure you can get away with it short term, but you may end up with an undercharged battery as a result. From what I see MMI reads 100pc at whatever state the battery is reconnected, but if the system believes you had your old 7 yo battery then it will probably not charge as it would your new one, and then under-charged batteries fail prematurely...

8R chassis, CAHA engine code. My alternator failed, battery collapsed, recovered from M3... Local garage and Audi West London failed to ID the fault, so I did my own research (after the same failure again). A. Replaced the 7 yo battery. Easy job, 10mm spanner to remove -ve then +ve terminals in the boot. Battery shd be the same spec, but you need to reprogramme the battery coding, for which you need VCDS (see Ross Tech forum). In theory you need to keep some power on the terminals under the bonnet to keep memory. 2. Use VCDS and run auto scan. CAN 19 measuring blocks 14, 15, 16 will give you Generator data (18, 19, 20 for battery) I had block 15 error in Electrical Generator status You can remove the regulator (VR) from the back of the Valeo alternator, but Q5 is tightly packed and you have mm' s to spare. Remove negative from battery (i didn't bother with a memory saver, no ill effects). Remove live from back of alternator, and plug... Take off cage with screwdriver. M7 to remove 3 bolts, remove VR. My brushes were gone, check out YouTube for an easy soldering job to replace... Wasn't my brushes though, then replaced the whole VR, not that either...still got the Group 15 fault. Just embarking on replacing the whole alternator. Again doable..but you'll need some dexterity. -Ve disconnected. Remove timing cover. Remove 2 bolts on coolant tube (black hard plastic), move gently sideways. Mark ribbed belt direction. Use a wrench on the tensioner to remove the belt from alt pulley only. Remove two screws, with a 13mm ratchet, on alternator bracket. Use a 19mm socket and a bolt to draw the alternator bushes out, its v easy . Bottom screw can not be fully removed, only once the bushes are withdrawn.... Audi service manual suggests tapping them out with a hammer - waste of time.... Remove the alternator from engine bay pulley first And...Valeo and Bosch are not interchangeable...diff plug for starters. Hope it helps