Flat battery after 4 days

B

barrywise

Guest
6 months ago, at the end of the winter, I noticed an occassional sluggish start up from a battery in poor charge. I assumes that the battery was on its last legs and got Audi dealer to fit a new one. Since then I have twice had a completely flat battery. This has happened after leaving the car for about 4 days, then trying to start it again. Back to Audi who said "Charge rate 14.5 volts. Battery at 8.4 volts - suggests battery fault. Give battery long slow charge, then see if fault remains." I pointed out that this has been going on for some time (probably even before the battery was changed) and I do plenty of 150 mile trips most weeks so a long slow charge will not tell us anything. They agreed to test for battery drain. Before I could get the A2 back to them the battery went flat again! Eventually they diagnosed a faulty central locking control unit and ordered me a new one to be fitted next week. They explained that the car goes through several checks once locked and shuts itself down to conserve power. However my control unit is faulty and is not shutting down properly.

Anyone else had this fault? Is this acceptable for a 4 year old car? Shouldn't a faulty control unit show up when the car is serviced (assuming the dealer does a diagnostic check during the service)?

Audi have quoted about £180 plus fitting plus VAT to do the work. I assume they are referring ot the unit under the passenger footwell. It looks easy to replace this myself and avoid labour charges. But the dealer said that the keys will need reprogramming, so I assume that I cannot fit the unit myself.

By the way, when the battery is flat, it is only possible to get to the boot by tugging the emergency release on the tailgate. This disengaged itself from the lock mechanism when I tried it. So I had to take the tailgate trim off to relocate the release tag. It was quite easy to do this. Brute force in a direction at right angles to the door did the trick (i.e. pull it straight off). To replace, locate the trim around the lock housing then hinge into place and snap the holding studs home.
 
Hi barrywise, welcome to the A2oc
I don't recall any other Club members reporting this so it's probably not a common problem.
At a cost of only £180+, I'm fairly sure it wont be the central comfort system module which is being replaced. In addition to this main unit in the passenger footwell, the front doors (and back doors with electric windows) have a control unit which is integral with the window lifter motor assy. It's likely to be one of these units which is faulty.
I think a diagnostic check is part of the service but I'm not sure if every single fault is recorded by the ECU.
Let us know how you get on

Cheers Spike
 
new control unit

Millhouse Audi (Bath) has now replaced the control unit (the first thing you see when you lift the passenger floor cover - "Zentrale Komfortelektronik"). They described this as the "central electronic control unit". Charged £194 for the unit, 2 hours labour @ £88 (this included diagnosing the fault). Plus VAT = £435.

The fitting work included re-coding the control unit and re-coding the door keys.

They said it is a rare fault and that A2's are generally very reliable!

It may be sometime before the car gets left for several days without use, so I don't yet know if this has worked. Fingers crossed!
 
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I had a similar fault on a Passat - stood for three days (it rarely did) and it would not start. AA man said battery was OK but flat, checks revealed nothing abnormal on (checked boot light, glovebox light etc). Battery given quick charge and checked again.

He was recording a 1.9A "everything off" current and didn't believe it - checked with his control centre and they confirmed an "everything off" battery load of 1.5-2 Amps - No wonder it ran down. Am amazed it didn't do it more often.

May be a similar issue with your A2 - anyone know what the "everything off" current is for the A2?
 
Hi barrywise
Thanks for updating us on the repair. The comfort module was less than I expected but the total cost is still rather expensive

Cheers Spike
 
happier battery now

Success! Car left locked for 4 days and then started instantly.

The dealer described the system as having a certain routine (and time) to go through to shut down properly. Things like making sure the internal lights are off and the alarm is set. Then the module puts the electrics into sleep mode so that the "everything off" current is very low. Apparently my module wasn't doing this and was keeping the electrics powered (I think he meant door lock solenoids energised, etc). Hence the battery drained down.

Any further info on this "shut down" routine from other members would be of interest. Or maybe no-one knows what an A2 really does when it goes to sleep? [Maybe it dreams of being an A6]
 
Similar problem with flat battery

I have a similar issue with my 2004 Tdi90. I was away for 3 weeks over Xmas, and the car started fine when I returned. However I thought it worth topping up and used an intelligent charger to do it, and the battery charged up fine with 2 green lights on the charger. Then I did a return trip from London to Wales a few days later so the battery ought to have been in good shape, but 4 days later it was flat, and I couldn't get it to fully charge i.e. no 2 green lights. I then read this post and thought I might have the same problem and had a static load test done which showed the current drain as very low (a fraction of an amp) so it doesn't seem to be that......but can a battery that was fine when left for over 3 weeks go off 3 weeks later?
 
battery problems

I would say that it is unlikely that a battery could go from being really good to being unable to hold its charge within a few days. I would get two things checked at a garage:-
1. The battery - a garage can check if it can hold a charge or will discharge quickly. They have a device to simulate a discharge and they can see how the battery handles it.
2. The alternator - if that starts playing up you should get a warning indication on the dashboard display. However, if it keeps charging a bit it may still be faulty and not show up on the warning panel.
Good luck.
 
Continuing battery issues

Hi,

I have now had a static load test done on the A2, and the drain was minimal, so it seems it is powering down correctly. However the battery still drains quickly. I have been able to recharge the battery to full (i.e. 2 green lights on the intelligent charger) but it still drains in about 5 days and I don't appear to have left anything on. The battery is about 3.5 years old, and was fine for 3 weeks over Xmas, so I'd be very surprised if it were the battery. The belt for the alternator is tight, and the red light goes ouit when the car starts so I suspect it is charging OK. All very strange. Any suggestions very welcome
 
Has a very similar problem with my '05 1.4 TDI, turned out that some fluid had been spilt into the radio in it's past and the power board (or something) had been corroded which was causing it to drain the battery. They pulled the thing out and it has not been a minutes trouble since.

Not sure that this helps, but it sounds like it is going to be an obscure reason like this.
 
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