Here are examples of messages that will appear if the Phaeton begins to shed loads.
Advisory Messages - Load Shedding
Volkswagen of America has recently released a Technical Bulletin (TB) to provide Phaeton technicians with more guidance - primarily a better overview - of the electrical load management function on the Phaeton.
As most of you probably know from having read the post Rear Window Defroster, our Phaetons have a very sophisticated system for shedding electrical loads to prevent battery discharge. It is a clever and well designed system, not at all unlike what is found on the most modern Boeing and Airbus aircraft. However - the energy storage capacity of a Phaeton battery is finite, and if the ignition is left turned on - without the engine running - for any period of time beyond about five minutes, the car will start to run low on stored electrical power. That is why it is so important to always have a battery maintainer hooked up to the correct location whenever work is being done on the car (see this post: NAPA Battery Maintainer for a Phaeton).
The attached technical bulletin tries to explain that if the Phaeton has gone into load shedding mode ('Intervention Load Management', to use the VW term) at any time in the past, a fault code will be stored in controller number 09 - the Central Electrical controller - indicating that load shedding has taken place. This is not a 'fault' per se - it is just a report that the Phaeton has, at one time or another, done what it was designed to do - shut down non-critical power consumers in order to prevent the battery from becoming discharged.
For us as owners, the trick is to try and avoid putting the car into a situation where it needs to start shedding loads. Load shedding itself is not a bad thing, and it is mostly transparent to the user. As you can see from the load shedding diagram, the least important functions get turned off first, and it is highly unlikely that we as owners would ever even notice that this is taking place. The big problem that we need to avoid is discharging the battery to the point that the car reaches the first critical low voltage threshold. We can recognize that this first threshold has been reached if we ever see a message on the Y24 display (between the speedometer and tachometer) that says PLEASE START ENGINE.
How do we, as owners, avoid reaching this level of battery discharge? It's easy, if you know how the system works.
1) Don't leave the ignition turned on with the engine off for longer than 5 minutes. If you need to leave the ignition on for longer than 5 minutes, either start the engine, or, hook up a battery maintainer.
2) If you or your Phaeton technician do hook up a battery maintainer, be sure to hook it up directly to the terminals of the vehicle power supply battery (the left side battery). Hooking a battery maintainer up to the terminals under the hood is (to borrow a simile from LBJ) like pissing down your pantleg - it might give you or the tech a nice warm feeling, but it doesn't accomplish anything other than that.
I've attached a copy of the TB for everyone's review, below. It does a good job of explaining how the load shedding system works, but (in my humble opinion) it doesn't make it clear to everyone how to avoid unnecessarily activating the load shedding system in the first place.
Example of a Diagnostic Report indicating that Load Shedding was active at some time in the past
Address 09: Cent. Elect.
Controller: 3D0 937 049 G
Component: STG.Bordnetz 5001
Shop #: WSC 01065
1 Faults Found:
00907 - Intervention load Management
000 - -
Truth is, this isn't really a 'fault', it's just a report that the load shedding system was active at some time in the past.
Phaeton Load Shedding Sequence
As you can see, the least important stuff gets dropped first. The car was designed so we as owners would not even notice when this is happening.
VW of America Technical Bulletin
Click on the link at the bottom of this post to download the PDF.
Last edited by PanEuropean; 04-13-2012 at 09:17 PM.
Here's a link to a related post that discusses J367 Battery Monitoring Controller Replacement. Several of us who own early production MY 2004 Phaetons that were originally equipped with the 'B' suffix Battery Monitoring Controller have found that replacing the B suffix controller with a 'C' suffix controller has improved the quality of the charge being supplied to the vehicle power supply battery when the car is running, thus solving all our problems.
I'm not suggesting that if you have a B suffix controller that you should run out and ask to have it replaced with a C suffix controller, rather, I'm suggesting that if you are encountering continual problems with intervention load management messages - such as the ones pictured above - appearing, and you cannot identify any more probable cause for the messages, such as leaving the ignition on without starting the engine, or only driving the car very infrequently (e.g. once a month or less), then you might want to consider reading the above referenced thread about the Battery Controller Replacement.
Whatever you do, DON'T accept the suggestion of the Guided Fault Finding (GFF) software on the VAS 5051, 5051b, or 5052 to replace the generator (alternator) on the car unless you can independently verify with certainty that there is a problem with the alternator. There is a known problem with the GFF software (as of summer 2005) that will cause the GFF process to recommend a generator replacement if it cannot identify any other cause of a discharged vehicle power supply battery.
I found this posting extremely informative, and will order the dedvice right away, since i plan to acquire the vag com as well. in your last posting you mention that even leaving the key in the ignition, without turning it, can discharge the battery - could you confirm this, as i normally leave the keys in the ignition for all my cars in the garage. with the phaeton so far i have not, because i suspected the presence of the key triggers much more than just a buzzer like other cars. However, this way I always end up walking to the car only to realize i have to go back inside the house because i don't have the key, so I was seriously considering reverting back to the old practice of leaving the car in the ignition.
Many thanks, as always, for your great postings, and best wishes of a happy and fruitful 2006!
Quote, originally posted by Motorista » ...in your last posting you mention that even leaving the key in the ignition, without turning it, can discharge the battery...
No, I did not say that (at least, I hope I didn't say that!). I believe another person posted that statement. The full explanation that I gave of electrical system behavior can be found at this post: click here, which I wrote in response to a question from Anton.
I am pretty sure that simply leaving the key in the ignition will not discharge the battery... I wrote: "If you close the doors of the car without locking the car, even if the key is left in the car the comfort bus will power down after 2 minutes have passed, assuming no-one remains inside and operates controls within the vehicle that would cause the comfort bus to remain powered (e.g. someone sitting in there listening to the radio)."
However, the action of locking the car from the outside (either with the keyless access button on the door handle, or by pressing the button on the key fob) does send a very definitive signal to the car that you are finished with it, and the car then 'goes to sleep' quite promptly.
You mentioned in an earlier post that your car was a 2005 model, if this is so, then you already have the 'C' version of the Battery Monitoring Controller. The newer version with the level 2700 software was cut into production towards the end of the 2004 model year - I think in the first week of January of 2004, but I am not dead certain of the date. So, you have no worries in that respect. If you have encountered battery problems, perhaps have a close look at the recommendations in the post I referenced above (the click here reference) - those recommendations are not simply mine, they are the collective wisdom of all of us on the forum, with the assistance of the electrical engineers who designed the Phaeton electrical system. We haven't heard of any battery related problems in the last 10 months, since those recommendations were originally published here on the forum.
Note that the above-referenced TB has been re-released, with some minor editorial chages. The latest version (ending in -06) is attached below.
Edit April 2012: The version of the TB attached to the first post above is the most recent version, ending in -06. Michael
Last edited by PanEuropean; 04-13-2012 at 09:19 PM.