BMW R1200RT/R1250RT Forum

Hi All,
I'm having a problem with the alarm on my '18 R1250RT going off seemingly at random. The bike is kept in a locked garage which is attached to the house and has both a CCTV & alarm sensor covering the inside of the garage so I know there isn't any movement going on, but every now & then it just goes off. As far as I'm aware there are no mice or spiders involved but when I cancel the alarm the red LED flashes once and this tells me it's Sensor 1 that's triggered it. So a few questions to the hive mind.

1/ What type of sensor is Sensor 1, where is it and if I have to replace it, is it a thing complicated to do and do I need a GS-911 tool to reset or register it?

2/ The manual talks about the DWA unit having an integral battery and allegedly there's a warning at start up if the battery start running low. I'm not getting this warning, but anyone know how long the internal batteries last & how to replace them.

3/ I've read about water ingress into the DWA unit, given the weather of recent (and the bike is kept in a dry garage) I doubt there's water in there, but if there is, is it just a case of removing the DWA unit, letting it dry & refitting or is it likely to be permanently damaged.

and
4/ For the moment I've turned the alarm to manual so it's not setting automatically and won't wake me up at 2.00am again, but the question is does the immobiliser still set itself? I've read the manual right it does as the immobiliser is separate unit to the alarm, but can anyone confirm this?

Any help, pointers etc much appreciated.

Can't answer the questions but do you keep in on charger? if so these can set some alarms off that sense voltage fluctuations

Stu wrote: Sun Aug 17, 2025 6:51 pm Can't answer the questions but do you keep in on charger? if so these can set some alarms off that sense voltage fluctuations

Yes, via one of BMW's own Charger Plus units plugged into the socket on the RH side of the fairing. It was certainly plugged in last night, at the other times, honestly, I can't remember.

leave it unplugged to see if it makes a difference at least just to rule it out

Stu wrote: Sun Aug 17, 2025 7:14 pm leave it unplugged to see if it makes a difference at least just to rule it out

I thought about that, but SWMBO really wasn't happy at two o'clock in the morning and I got he the why I haven't you sorted this out yet lecture. I'll be in the dog house if it goes off again in the middle of the night again.

Mine used to do same. Was told by bmw mechanic that water gets down between back of seat and rack and he has seen alarm filled with water. had mine replaced and always wedge cloth back of seat when washing. New one does it occasionally as often find red light flashing when ignition turned on. garage not in earshot. Never has been on trickle charger. Alarm was an option so guess not linked to imbolizer.

BoB21 wrote: Mon Aug 18, 2025 7:41 am Mine used to do same. Was told by bmw mechanic that water gets down between back of seat and rack and he has seen alarm filled with water. had mine replaced and always wedge cloth back of seat when washing.

Interesting as I'd wash the bike that day. Whether the seat/rack gap got any wetter than normal I can't say, but I took the seats for a a quick look in the cubby hole the alarm sits in and it all looked dry, but then it 48hrs since I washed the bike and it's been sat in a warn, na at times hot garage.

Sensor 1 is usually the tilt/movement sensor, so sometimes even small vibrations can set it off. A weak DWA battery can also cause random triggers even without a warning on the dash, so worth swapping it if it’s a few years old. They’re not too hard to change, just tucked inside the unit.

The bikes in a locked garage on it's centre stand so there won't be any movement, but no doubt about it, the DWA unit will have it's original batteries in it. I bought the bike at three years old, it'll be 7 years old in a couple of months and that's pretty good going for any battery. It's only 2x CR123A type batteries held behind a 4x hole screw down cover, sounds simple enough, but to get to the unit looks like I've got to take the rack, grab bars and several other bits off as well. They're going to need replacing at some point soon so I'd rather do it on a nice summers day rather than freezing my nuts off under artifical light in the middle of February. Job for Saturday morning I think.

ta.