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E39 Car alarm going off randomly?

80K views 96 replies 44 participants last post by  mattmar1 
#1 ·
Does anyone have any ideas to what is causing the problem and maybe a solution to fix it.?
 
#2 ·
Its your interior sensor, buy a new one and your done.
 
#3 ·
Before making any assumptions and shelling out $$ on an interior sensor, try disabling the under-hood sensor. It's a hugely common problem on E39s.

Lots of discussion on it here:

Hood Sensor / Alarm issue

Try pulling the plug. See if the alarm still goes off randomly. This doesn't affect your main door/interior alarm sensors in any way.
 
#7 ·
#9 ·
same prob here but on a E38.. Q, do you have a pic of the e38's hood sensor? from what i gathered, i disconnected a wire going from the top right bay into the hood. (driver side)
 
#10 ·
The e38 hood alarm switch is up by the expansion tank for the radiator...if that's not what you unplugged...I'd plug it back in. :D

 
#13 ·
Check your battery voltage too; the alarm is designed to go off if it detects that there's a variance in the battery current in order to prevent battery tampering.
 
#14 · (Edited)
Hey all - Having the same problem... Replaced the battery...

I don't have the switch like Dking078 on my 97 528i - but I did unplug the one I have like QSilver7 and the alarm still went off randomly shortly after. Is there another hood sensor i should look for? or is that difference in years?

Otherwise can I disconnect the interior and be done with it?
 
#18 ·
My alarm was driving me crazy one night a few weeks back. Apparently a cicada entered into the car through the cracked sunroof and the interior poxy sensor set off the alarm every hour or so from the damn bug flying around. All is well now though ;) I know if you double press lock it disables the proxy sensor...not sure if it does anything else
 
#21 ·
No, not the microphone... There is a motion sensor in the car. I bet Q has a picture of it lol... But to disable it just press the lock button on your key twice. (Press.... 1 second pause.... Press again)
 
#25 ·
i once had a problem like this...hehe.. it turned out i left my cellphone in the car... and people were rining me... i would goto the car.. disable and re-arm the alarm...
true as bob later on it would randomly go off again... only LAAATER when i was looking for my phone did i click what had happened.,
like 8 missed calls on my cell. around the same amount of times the bloody alarm went off...lol
 
#26 ·
I had the problem of the alarm going off when I was parked on a slight downward slope, and passing traffic would generate enough road vibration to set off the motion detector. Once that was disarmed, it was fine.

Also had the problem last week in the middle of the night as my battery was apparently going dead from an unknown/undetected drain. Finally had to leave it unlocked in my driveway for a few hours until I got up and recharged the battery.
 
#27 ·
+1 on the cell phone bit!!! I have a blackberry and left it in my 540, it didn't just set the alarm off when it rang, but even when it was searching. I'm wondering if maybe the infared is setting it off. by the way, just to make sure, i placed my daughters regular phone in it and it did nothing.
 
#29 ·
so i have been having the same problem mentioned a few times in this post.. i took out the fuse by the battery.. and now the alarm obviously doesnt go off but when i lock the car.. after a few minutes.. the lights start flashing as the alarm going off except the sound.. any suggestions?
 
#32 ·
I had my truck open on its own once and set the alarm off. It just went off again last night in the garage (only the second time ever), and while I played with the trunk before leaving for work I don't know for sure if that was it this time. Hood sensor, hmm...
 
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