X164 GL320 Random Alarm

[hamazz]

Got a problem with my GL, the battery ran flat whilst i was away, when i got back i put it on full charge, a week or so later the alarm would randomly go off at night or middle of the day.
These GL dont have the alarm unit under the wheel arch as other models like the ML had. i pulled fuse 110 which was for the alarm for a week and it did not go off, however the headlights stopped coming on when unlocking the vehicle and now only stay on for a short while after locking the vehicle, not sure what the relation is here....

Alarm went off again today after i replaced the fuse yesterday to test something, One of my key fobs would not unlock/lock doors, replaced the battery in the fob, but had same problem, however would start the vehicle with no issues, after alot of messing around between both fobs, i got both to work and lock/unlock the doors.

Has anyone had something like this happen, where one fob would not unlock/lock then would randomly work again.

Would anyone have an idea what could possibly be triggering the alarm, i have checked all windows are shut and all doors are properly closed, not sure where the sensors are in the doors to check them

Hamazz

 

[KillerHERTZ]

It will be the alarm's own internal battery. it might not be in a wheel arch, but it will be someplace.

 

[sweeper]

I disagree with the internal battery thing, best way is check the log of alarm events using a suitable diagnostic tool, icarsoft will do that, on the R class I found it was the rear window circuit, to be exact it was the left rear side window, I was able to disable the circuit by disconnecting the wire from the overhead control panel which is done in the boot area, right hand side behind the rear light (or in front whichever way you look at it) this cured all my random alarms without affecting the motion sensors, interior sensors etc.
I'm sure the alarm unit will be under inside the front wheel arch, left hand side, the later ones have the battery away from the circuit board and are less likely to cause any damage, I removed mine completely but was still getting alarm activations (shown on log) I even cut it apart and checked the battery was ok, I think this faulty was on earlier types where the back up battery was soldered to the circuit boards.
What model year is yours I can take a look at where the alarm is and the wiring diagram, the GL ML and R class are all very similar cars, the alarm consists of the unit and uses the several of the control units around the vehicle (front and rear sam I think) so there isn't just one alarm controller, the alarm unit doesn't control any alarm activation, so if you unplug it the alarm will still activate, you just wont hear it. (mine didn't even go off when I removed it, I thought it might be tamper proofed)