'96 SL500 MBSS Siren comes on

[MD5]

The alarm siren randomly came on whilst driving today. The car is fitted with the MBSS system, with the red and green lights in the rear view mirror. Whilst the locking functions work fine, and the immobiliser comes on as it should etc, nothing I did could switch the alarm off, including turning off the engine, removing the key, locking, unlocking and restarting again. It finally stopped after what sounded like the comedy death throes of a police siren submerged in water.

I'm wondering what triggered the alarm coming on, and whether or not anything more sinister awaits. The siren I can live without, although it may be serviceable from what I've googled with its part number, Q3 50 06364, and it has its own battery. Any thoughts please, anyone?

 

[Dec]

Do you have a round? key for turning off the alarm?
What type of remote/s do you have?

Dec

 

[MD5]

Dec, it's exactly like the key in your image, a solitary, single buttoned fob with a fold away blade and integral infra red remote control.

 

[Dec]

It shouldn’t be going off when you are driving as it should be disarmed when you unlocked the car.
If there are rechargeable batteries within the siren then that’s probably where the fault lies.
There MIGHT? be a key switch, concealed by a weather bung on the siren, if you have no key for this key switch, then perhaps you could turn off the alarm system by opening the siren and bypassing the key switch… if you have one!

You could unplug the siren but that wont cure the faulty alarm system.

Another possibility would be to try Scorpion alarms to see if the have a replacement siren, Scorpion alarm… Scorpion Automotive - Supplier and manufacturer of vehicle security alarm systems and mobile communication Interfaces - Contact Us ... but that is just guess work and might not solve the fault.

Dec

 

[MD5]

Thanks Dec. I read elsewhere that the red/green i/r mirror system is a factory fit, but parts beginning with Q are dealer add ons, suggesting the siren was added later. Hopefully, replacing the batteries may be the fix, but I was curious as to what would trigger the siren whilst driving. To be honest, it was so unobtrusive and we were driving along a high street, I thought it was one of the shops!

 

[Dec]

One of the triggers for an alarm to sound is if the alarm is tampered with and someone disconnects the power supply to the alarm. If the siren batteries are disintegrating then the alarm might see this as tampering and so it sounds off. Example below, different siren but same princaple.

There could also be damage to the printed circuit board inside the siren which might be causing the fault too.

Nearly all MB dealers fitted Scorpion alarms around the time your car was available.

Dec

 

[MD5]

Until recently, the car was at my father in law's, connected to a battery conditioner, which became disconnected for a few months. I recently bought a new car battery, and brought the car home now that I have suitable garaging again, so I'll check the internal batteries when I get a minute.

Thanks again.

 

[BTB 500]

Thanks Dec. I read elsewhere that the red/green i/r mirror system is a factory fit, but parts beginning with Q are dealer add ons, suggesting the siren was added later.

MBSS was fitted when the cars were delivered to the UK. I've got paperwork with my '97 car showing this being done.