Berny9621

In September i bought a well maintained (aside from the Homelink, Auto Headlight sensor, and mirror dimming not working, and the rear sunshade button wouldnt do anything) 2004 Audi A8L 4.2, recently i took it to the Audi dealer to have the timing belt service done. The same day but a couple hours later the check engine light turned on but the car ran as normal, i took it in and had the camshaft position sensor replaced [$410] plus a 55k service recommended by the consultant because "i wasnt the original owner so i dont know the real history" (funny because i have record of all oil changes and the air suspension being replaced in 2015 by the previous owner). The car came out with a clean bill of health other then looking a getting the suspension bushings done in the distant future. Last week i backed into a tree and it removed a tad of paint and looked like it pushed the bumper out or it couldve always been that way. However today, randomly; after driving all day in pouring rain, the power steering crapped out and the car stalled. It struggled like a car with a crap battery 3 times before starting. When it did start all the accessories that didnt work before suddenly decided that they wanted to, and stayed working after i restarted the car 2 times (ran like normal and no issues then) also while it cranked and died those 3 times the passenger seat made a popping noise. Any idea of what it could be?? If this helps if i go into the MMI and turn off ECON, it swiches to ECON on immediately and i was driving all day with the sunroof on vent because the blower motor died and it pulls air through the vents at any speed; simulating the blower motor running. Thank You for your help!

Berny9621

Also i just checked the vent flaps in the battery compartment and it appears a tad of water is on the flaps.

MP4.2+6.0

Not sure I follow al the ins and outs of this. But many of us will tell you that bottom line a D3 can have lots of weird electronic hiccups with a bad or failing battery. Sounds like just from the cranking you sense you may have one. If battery is more than about 3 years old, I would replace it. If unknown age, same answer. My rule is one and only one unexplained battery related incident allowed where I need to charge it. That is, anything but owner screw ups like laving lights on. Second incident leads to immediate trip tp get a new one.

Realize too that car has a power management system, so when it thinks battery is low it cuts off power to things classified as not essential. First to go are things like keyless entry, then the remote fob entry. By the time it's done, most anything non critical like ignition, lights, etc. get sacrificed. You may be running into this too.

Net, probably get a new battery. Easy self install since right there in trunk.

Berny9621

Even though the battery meter in mmi says its @80%? Basically Auto headlights, homelink, rear dome sunshade button and the red dome lights didnt work before the stall and all of sudden they do. Also the vent in the battery compartment looked like water got in it and we had the timing belt change done 3 weeks ago on the dot.

Jack88

Timing belt change is likely unrelated, there's nothing easily damaged doing it to cause your symptoms, at least that I can come up with. The battery meter in MMI is more or less useless, so ignore that and go by the symptoms. MP4.2 is right on the money, these get very weird when the batteries start to fail.

Berny9621

Ok, does it have to be a VW/Audi battery or can i go to say, a batteries plus and get it replaced in 30 minutes with free install as opposed to the dealer for whatever and not having my car all day?

MP4.2+6.0

Battery meter is a joke said bluntly. If it says anything but 100%, yes there is likely an issue. Honestly, that is its only function I found in 9 years and 100K miles. And usually when it wasn't 100% for me, it was sort of well duh, like leaving lights on, having ignition on for an hour testing things, etc.

I would have to look it up, but the kind of things you cite as not working are exactly the kind of thing the power management system cuts off if it thinks battery is low. Think about it--all discretionary first world luxury stuff basically, not anything car truly needs to get you home.

Batteries are maybe $120-175. For dealer to even look at it will cost you more than that. And being stranded in some godforsaken parking lot at 10 at night (or 1 or ____) and rain or snow or wrong part of town or... No brainer to me.

No, should not be water back there. If you mean inside the battery vent tube, then no big deal. But if you mean any obvious water down in that area below battery, needs attention. Search or review posts in just last week or two. I gave a long list of areas to look at. But, unrelated to kind of stuff you are describing, other than it should be attended to or other electronics could be compromised.

Timing belt work has no logical connection to this. Even if they screwed up big time and didn't put accessory serpentine belt on right (which is in front of timing belt), you would have a dash light show for that. If you did lose power steering though and you have a light for alternator charging type issues, definitely look and be sure serpentine belt is in place. Easy to see in front of motor. Timing belt is hidden under covers, but serpentine belt is in plain sight. Assuming it is in order, I wouldn't dwell on it much. Dead batteries are dime a dozen. Every 4-7 years on an Audi is decent life. Honestly, as a 2004, you should be about on your third one about now.

Berny9621

Ok, thank you for the help!

MP4.2+6.0

You can get battery most anywhere. Just should be correct fitment. Get the "big boy" (larger) size if you don't already have. The space and clamp will fit any of the sizes for D3's. Most auto parts stores have them on the shelf these days. Even Home Depot may--where I got my last battery for a Mini aka BMW)... Or, Heaven forbid, Wallyworld, K Mart and the like for that matter. All batteries are made by essentially three companies--Exide, East Penn/Dekka, and Johnson Controls. Another of my deep dive posts if you search for it. The Audi dealer ones (Audi branding ,or Autobahn, or Varta) are most likely Johnson Controls. Sears as an example were often Exide some years back, but now more likely Johnson Controls. Interstate is Johnson Controls IIRC. Many of the store brands are Exide, either labeled as such or store brand. They all work; newness and capacity are the most important factors grossly simplified if you basically want modest $ for a now older car.

You are supposed to code the battery to the D3. But what most DIY'ers do with store batteries who have the VCDS diagnostic cable and software is just add one to their prior battery serial #. Or, if you don't have access to the VCDS diagnostic tool to code it, frankly most of us believe (or have experienced) the power management system eventually figures out that you have a new battery with no special coding and thus more reserve capacity, and then adjusts (dials back) its power shedding algorithms to match. My Mini had the same stuff (and folklore around coding). Handled the Exide from the Home Depot shelf just fine. I kind of figured it would, since when I puled off the Mini original battery stick on cover label, it said...Exide.

Berny9621

MMI shouldnt need to be recoded? Any special steps i have to take or just disconnect and swap like a normal non german car?