Good Morning.

[Geoff Cooper]

I have had a 1999, 1.9 ltr Z3 for 6 -7 years,76k miles, and it has developed a couple of seemingly untraceable faults.Firstly, a battery drain .No apparent reason,if it is not started for 3-4 days power has gone. Secondly, the airbag light is permanently on.It did strike me that these two faults may be connected. Grateful for any in put.

Geoff Cooper

 

[Nodzed]

First step, obvious one, check the battery condition.

 

[Geoff Cooper]

New battery !

 

[t-tony]

Try disconnecting the alternator while the car is stood, it is possibly the cause of a drain. Make sure to isolate the terminals (wrap some cloth around it) so it cannot slip and “reconnect”.

Tony.

 

[Ianmc]

I had a similar issue with our E36 convertible. The battery while sound, would drain after a few days and the car wouldn't start. The door lock catch (fixed below the B pillar) contains a little switch that had failed (same part on Z3). Consequently, footwell lights were staying on and causing the drain. Not the most likely reason perhaps, but worth checking after the more obvious.

 

[Eddie Zedder]

A common fault is the boot light staying on when closed. Easy to check by dropping your mobile phone in there when on record.

 

[Stevo7682]

Does your zed have an aftermarket radio.
These have also been known to cause parasitic drains on electrical systems.

Airbag light could be connected but it will need a diagnostic tool to read the fault codes and perform the reset.

Stephen

 

[Geoff Cooper]

Stephen,that is starting to make sense.I replaced the original radio (which I still have) with a Sony CD. Thank you.

 

[t-tony]

Did you use an after market wiring adapter Geoff? I did (from Halfords) when I fitted a Sony unit in my 2000 Z3 and never had this issue. But, easy enough to test, just pull the unit and disconnect the block connector when the car is to be stood.

Tony.

 

[Geoff Cooper]

Thank you Tony.My Sony came from Halfords as well.I will certainly try your suggestion. At the moment I just disconnnect the negative lead on the battery when the car is standing.......

 

[t-tony]

It's worth trying different things to try to pinpoint where the issue is Geoff. Good luck and please keep us posted.

Tony.

 

[Geoff Cooper]

Will do.

 

[NZ00Z3]

There is a slight draw on the battery all the time. It's about 40 mA. Easiest way to find the culprit is to connect an amp meter (mutli-meter set on amps) in line with the positive battery lead, so all the current goes through the meter. Turn everything off and slowly pull fuses until you see the current drop. You've also got to remember that the car will be drawing more than 40 mA while it is "awake". So when you get it down to around 200mA, you have to start to let the car go to "sleep", which takes 5 minutes or something like that, between fuse removals.

For the airbag light, you'll need to get the codes read with a scanner that has BMW software. A normal OBD2 scanner will not read the airbag module.

 

[jaguartvr]

Check the door catch switches on the B posts. They can get sticky and it can be hard to see if the interior light is on in the car as it's so pathetic.

 

[Geoff Cooper]

Thanks to everyone for taking the time to offer advice.I will persevere !