[Phillip Biggs]

Hi, I hope someone can help. I've a 325ti SE Compact E46 with a factory fit alarm. The day before yesterday the alarm sounded without cause. I went to turn it off but found that all the car electrics were dead. No remote key operation, no lights on turning the ignition (although I think the air bag glowed dimly).
I pulled the negative off the battery. The alarm continued for a few minutes then went off. I put the battery on charge for about 8 hours but I'm not sure it needed it as the battery is only 5 months old and the charger needle didn't seem to move much.
Anyway, when I reconnected the battery the alarm sounded again, but this time when I turned the ignition the alarm went off and I had all the correct lights back on the dash. So all is well???
My question is, what caused it? Is it just the car electronics getting itself knotted up and my actions reset it and it wont happen again, or is it some electronic problem somewhere?

 

[Phillip Biggs]

Alarm sounded again, battery appears flat

Since I last wrote it's happened again. This time I disconnected the battery to stop the alarm, waited a couple of minutes and then reconnected the battery. Still dead - but at least the alarm didn't sound again. I noticed as I reconnected the battery that I didn't get that little crackle as the terminal touches. So I removed it again and just gently touched it trying to create a spark. I got one faint one and then no more. I recharged the battery during the next day and it's been OK since. So far. I've checked both battery connections are tight and went to a garage where they put a tester on it which said the battery was "good". It should be it's only 7 months old. Has anyone heard of anything that can drain a cars battery when it's not in use?

 

[Phillip Biggs]

Update - good news?

Hi, I thought I'd post an update. The problem hasn't happened again. Now I'm not sure about this, but I know at the time I was wondering what could drain the battery while the car is not in use and perhaps the only thing I could come up with other than start pulling fuses was to turn the headlight switch to the off position rather than leave it in the automatic position that I normally leave it in. I don't remember doing that but the switch is in the off position and I haven't had the problem again. QED? Anyway, I'll sort out the new problem I've got with the car (unrelated I think) and once I'm happy that's fixed I'll turn the switch back to auto and see if my battery goes flat again.

 

[witeshark]

Have the headlight auto relays been checked?

 

[Phillip Biggs]

Have the headlight auto relays been checked?

No. Where is it and how do you test it?

 

[witeshark]

I'd start with realoem.com

 

[Phillip Biggs]

Over a year later and it's happened again at about 7:45 in the morning. The car has been parked outside, as it was last time the problem occurred, but was fine yesterday when we went to Truro. I checked the battery and got 5V across it. I then connected the battery booster, which had 13.5V charge according to the inbuilt meter. That made no difference. Still no console lights, apart from that dim airbag one, and of course no ignition and the alarm continued. So I disconnected the battery again, both terminals, and the alarm stopped. 5 minutes later I thought to check the charge on the battery with my meter and it read 10.5V.
'witeshark' suggested headlight auto relays, but I can't find any information on that. Has anyone any other ideas on what can drain a battery - to the extent that the alarm believes it's been disconnected which is what I believe is happening - without blowing any fuses in the car?

 

[Jack Dabsy]

Firstly - Your alarm is doing its job, if it finds a voltage drop it will activate !
Secondly - Assuming that the battery is a good one, then there has to either be a short/faulty relay or a recurring bad earth...
You really need to have it read for some codes mate, this might be quicker than tracing dodgy earths etc...
HTH

 

[Phillip Biggs]

All done in this thread.

I thought it would be good form on here to let the people who have helped, or who were reading this with a similar problem, know what the final 'solution' was.

It was nothing more than a drained battery! My mileage since I moved to my new house has been lower and the journeys I have been taking have been shorter. Both bad for recharging the battery. On top of this due to my garage being full of stuff at times after the move and during DIY projects, the car has been left outside and locked. i.e. with the alarm on, as opposed to being in the garage and unlocked.

Now although I knew about these things, it never occurred to me that a fairly new battery could run down so quickly. I think the alarm being on was the decider. I never had the problem starting it when the car was in the garage.

So now I have bought a Ctek CTE-XS800 Car Battery Charger. This is a trickle charger that can be left connected for weeks or months and doesn't require you to disconnect the battery, so it takes moments to disconnect and connect before and after a trip. It keeps the battery charged up to exactly 12V (as read from the instrument cluster) and seems very sensitive. When the green light is on to say fully charged, just opening the door is enough for the light to turn red. So I can recommend it to people who are comparatively low use car users.

 

[Jack Dabsy]

You still need to conquer the power drain mate ;-)