What's wrong with my BMW alarm?

F

Flycaster

Member
 Boynton Beach, FL
When I got my Z4, I had put in original a BMW parts alarm system-the full system which included the cabin motion detector. System has worked fine for these three years, however today it acted strange. About 10 minutes after parking the car with top up and windows closed, no other cars near mine, no one touching the car, a friend told me that the lights were blinking. Pressing the key's open door button, shut the alarm off. I opened and closed the doors and reset the alarm with the key. A few minutes later that alarm sounded again. This time I opened and closed doors, the trunk and the hook, set the alarm. I think it went off again. Did every thing again, and it didn't go off. Drove home about an hour after all this started, while in the garage with the top up and windows down, I set the alarm. That was 4 hours ago and no alarm going off. Could you tell me what may have set the alarm to malfunction? Loose wires? I doubt it as all wiring is done by BMW connectors. Could it have been some kind off electric/microwave signal in the area? I've been parking the car in this area for three years without this problem.
 
On the Z3 a common problem was the hood sensor to malfunction and the alarm to set off. I took a quick look the other day to IMZ4N hood sensor and it appeared terribly similar to the on the Z3... If it happens again I would unplug that sensor (when the hood is closed the contact should be open so unplugging it should work; otherwise, if it's the other way around, you can hold it tightly closed with some electrical tape... Once you got it diagnosed it should cost ~$15 IIRC) and see if it still does it.

Hope this helps...
 
Yes - the hood sensor failing is a common problem on Z4's. Same happened to me and I just replaced it. No problem since. There are threads on the board about it but it's simple to replace. Located at the rear of the engine bay at the point where the 2 strut braces meet.

Some have reported success simply by bending the bracket slightly to get a firmer contact/press.
 
MRol said:
Could be a moth inside your cabin space?
Click to expand...

Not with the top open, nor are the sensors sensitive in any way.

99% the bonnet switch, replaced mine on the X5 as well when it did exactly what you described.
 
pvr said:
MRol said:
Could be a moth inside your cabin space?
Click to expand...

Not with the top open, nor are the sensors sensitive in any way.

99% the bonnet switch, replaced mine on the X5 as well when it did exactly what you described.
Click to expand...

He did say with the top closed and there are some frickin big moths in Florida... :poke:
 
cj10jeeper said:
Yes - the hood sensor failing is a common problem on Z4's.
Click to expand...
:headbang: :headbang:

I guess they used they end up hiring the summer intern that designed it for the Z3...
 
I do not doubt that it could be the hood switch. I jiggled the switch a few times and since then the alarm has behaved itself for the last 24 hours.

However, if it is the switch, what's the part number and where cn I get a replacement?
 
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