Alarm Going Off

S

skelters

Veteran
 Greenock, Scotland
3 times today the alarm has went off.

Never heard the alarms going off on the other two BMW's I've had.

Seems to be the wind causing it.

Few weeks ago it went off when a seagull flew really close to it.

Is this a problem as I'm finding it a pain in the Ar** checking the car.
 
If it happens during windy days it could be air blowing in through the heater vents and setting off the interior sensors. Not sure about the seagull though!
 
The wind is blowing towards the rear of the car tonight. Already went of twice tonight and once this morning.
 
In zed 3's the classic is the bonnet sensor playing up, £7 for a new one and 2 minutes to replace, worked on my Zed 3 last year
 
Kick It real hard!!!!!!!! :lol: then put duct tape over the dent :thumbsup:
 
muppet said:
In zed 3's the classic is the bonnet sensor playing up, £7 for a new one and 2 minutes to replace, worked on my Zed 3 last year
Click to expand...
Mine had exactly the same symptoms - bonnet sensor too.
 
Yep same on me Z4 3.0....replaced the bonnet sensor and never had a false alarm since.

It's scary to hear that the bonnet sensor on the Z3, Z4 and the X5 all exhibit this problem....what the hell is BMW quality control doing??
 
Excellent.

Although it also goes off if there are loud noises.

So that's only,

Road Tax due,
Window knackered,
Brakes need done.

Apart from that it's a great car until the Dealers break something else! Might be the car I've loved the most since I got it but I've had more problems than any other car I've had.
 
Hi all,

My alarm started going off for no apparent reason yesterday. I operated the bonnet sensor a few times by hand and it seemed to cure it for a few hours, but woke up this morning and there was a faint chirp coming from the car and a battery so discharged the car would not start. Unfortunately the local BMW dealer doesn't hold these switches in stock, so is there any way of bridging contacts etc that will isolate the bonnet sensor problem for a couple of days?

Thanks for any help.
 
Ah.. good old WD40. When I bought this car last year I thought the days of spraying the electrics with WD40 when the cold weather arrives had gone.
Still, it is the first thing that's gone wrong in 15 months of ownership, so I shouldn't winge.

Thanks for the tip Wondermike and I hope you're enjoying your SLK. I'm very tempted to p/x the Z4 for a 2002ish 500CL as I haven't had a Mercedes for a while.
 
This alarm is really doing my head in now so I took the bonnet switch apart to see if it makes or breaks the circuit with the bonnet closed.
It seems it breaks the circuit if the bonnet is closed, so in theory simply leaving the plug off the switch should prevent the alarm from being triggered. I've tried this, but without success - and the switch seemed in good condition inside, so I'm wondering now if it could be a boot or door switch or somthing else?

If anyone could tell me where these other switches are located I would be most grateful as I'm reluctant to leave the car unlocked until Monday or whenever BMW can look at it (on the assumption that the new bonnet switch wont solve the problem).

I've checked for any obvious electrical drains such as lights, ipod.
 
The other sensor that may be playing up is the "tilt sensor"...this is a considerably more expensive sensor to replace and its located close to the rear wheel well from memory...sorry I don't remember which side its on...I recall someone posting some BMW tech documents on it though in the old Z4um forum so someone else might know..

Speaking of Z4um...as much as I love z4-forum I've noticed there isn't as much technical postings/How To's being contributed which is a real shame as they are a fantastic resource for Z4 research...
 
Thanks drzed.

I substituted a good bonnet sensor from another Z4- alas the alarm still sounds within a minute or so, also I had a look at the owners handbook which mentions that if the alarm ecu thinks somthing has been left open a sequence of rapid flashing reports this from the LED under the mirror. I should have checked this before taking apart the bonnet sensor!
I suspect that the car battery may be discharged or on the way out, or possibly the rechargable cells in the alarm module. The car is a March 2004 reg with a build date of oct 2003 and has only covered 21,000 miles so the batteries have taken a bit of a hammering, particularly in the last six months with very short drives every couple of days. It seems odd though that the battery can start the car but drop its voltage quickly enough to trigger the alarm after being parked.

Luckily I've found that if I lock the car with the key the alarm (and LED) aren't activated, so at least the car can be locked even if there is no alarm protection. I don't know what the score is with regard to the immobiliser in this situation though.

With regard to Z4-forum and the tech. log I imagine it will take quite some time to develop a resource as comprehensive as the old Z4um. A lot of us here proberbly know the answers to a lot of the common problems and are au fait with the popular modifications applied to the Z4 through the old Z4um. As new blood finds this superb site the questions will be asked and answered by us and in the fullness of time I'm sure there will be a huge database of info. here.
 
Nick C said:
...I'm very tempted to p/x the Z4 for a 2002ish 500CL as I haven't had a Mercedes for a while.
Click to expand...
Very nice, let us know what you do about getting it, always a home for you in "Other Marques".

Sorry to hear it's still not sorted, although AFAIK the immobiliser will still be activated even if you dsable the alarm, so you should be OK until BMW get a look at it.
 
Mike - thought you chopped in the Merc for a Honda 2000????? Or am I running behind (again ...)
 
This is just an update in case anyone is having persistant alarm problems. Since having problems with the alarm from October I got used to activating the lock button twice to suppress operation of one of the sensors (either tilt or volumetric, possibly both?). In doing this no false alarms would occur. I was also having problems with the original 75Ah battery being on its last legs.

A few days ago I shelled out £112 for a proper BMW 80Ah battery and low and behold the alarm fault has dissappeared! It would appear that one of the sensors mentioned above are particularly sensitive to battery voltage.

The uprated (80Ah) battery is now recommended for the 3.0 and is wider by approx. 1" so a plastic spacer/clamp has to be removed before it will fit.
I'm pleased because this has been the only problem I've had with the car and ultimately it was down to the replacement of a consumable service item.
 
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