202 Alarm Going Off

[stevesey]

Alarm just went off for no apparent reason - also did it in the middle of the night last week. Any ideas? I will check the battery voltages at the weekend, but it's only 18 months old so I doubt it's that.

Obviously if it's going to start getting worse I'm not going to be popular with the neighbours.

Is there a tale-tell that it has been triggered when you unlock? Vauxhalls would typically flash the indicators four times rather than twice if the alarm had been triggered while you were away - wondering the Merc's do something similar (yes I should go and RTFM).

 

[Dec]

When you read TFM there should be instructions on how to turn off the internal motion sensors, probably via the key fob, your car is later than mine so cant advise on how this is done.
If this solves the problem there may also be a way of reducing the sensitivity of the motion sensors to allow there use again.

I’m assuming that the motion sensors are the problem, other things to check are under bonnet alarm pin switch and door/boot pin switches.

Others might be more useful and have better suggestions for you.

Dec

 

[grober]

In the past people have been troubled by spiders triggering the internal sensors. Sounds like an urban myth to me but who knows? Switching off the internal motion sensors may help to narrow it down?

 

[Simon]

Not very clever I know but I took the fuse out of mine, it can be found in the boot fusebox.

 

[stevesey]

Went off again at about 01:00am - so I RTFM'd and turned off the tow away and internal sensors. I will have to try this for a few days and then try each individually to see if either of them make a difference.

I'll also be on the look out for and infestations

 

[GazCaff]

make sure your seatbelts are retracting properly too when you get out of the car. They can trigger the motion sensors if they move afterwards.

 

[Spinal]

Issues I've either had personally or have heard of with W202 alarms:
- Wind causes dust to move in the car activating motion sensors (fix: close air vents before leaving car)
- Spiders/insects in the car (fix: "tune" motion sensors, knob on the back)
- Heat causes air to move in car, thus moving dust (fix: point motion sensors down at dash or tune on back to lowest setting)
- Doors not read as closed (check door sensors)
- Thieves stealing the car (fix: big gate, guard dogs and a shotgun)

M.

 

[stevesey]

- Spiders/insects in the car (fix: "tune" motion sensors, knob on the back)
- Heat causes air to move in car, thus moving dust (fix: point motion sensors down at dash or tune on back to lowest setting)

Are the sensors on the B-pillar tuneable? Mine aren't pointable.

 

[Koolvin]

On my 1997 if you hold down the unlock doors button from the dash for a few seconds then that will temporarily disable the motion sensors for the next time you arm the system... (however yours is a facelift so may be different)

 

[stevesey]

On my 1997 if you hold down the unlock doors button from the dash for a few seconds then that will temporarily disable the motion sensors for the next time you arm the system... (however yours is a facelift so may be different)

Yep - facelifts have a button on the dash to disable the interior sensors and/or the tow away sensor. Was RFTMing at 1:00am to check how to use it.

 

[KillerHERTZ]

Mine went off at 05:40 this morning It always happens when the weather gets warmer for me - about twice a year.