Interior motion sensor too sensitive?

[Kingpin!]

Hi, forum!

I think I have discovered that when my internal heater is on (to warm up the car for a couple of hours so I get ice-free windows in the morning (which in turn is connected to an internal 240VAC outlet on the passenger side)) then the alarm might go on. I also think that if I set the interior motion sensor to off then the alarm stays quiet, at least that is my belief so far.

So, my question is if this behavior is normal - is the interior motion sensor so very sensitive that a heater which just contains a heating element, a blower fan, operating indicator (LED) and standing on the passenger floor might trigger the alarm?

Is it something that can be adjusted (software update even?) or does it indicate some sort of fault/defect?

I would like to have the interior motion sensor set to on by default setting so I don't have to think about activating it all the time when I really need it, even though this option comes up on the display after I turn off the ignition every time.

The car is a 2006 R-Class.

TIA!

 

[richard]

Are you sure its the IMS ?

It could be that the battery is getting low. If its the original from 06 its very likely due a change and a heater will be taking an electric reasonable amount of current.

R

 

[Kingpin!]

Are you sure its the IMS ?

It could be that the battery is getting low. If its the original from 06 its very likely due a change and a heater will be taking an electric reasonable amount of current.

R

Thanks, Richard, but the heater is supported by the internal (external actually) 240VAC outlet on the passenger side so it isn't using the internal battery.

 

[richard]

OK

The other thing that happens at this time of the year is Spiders. We see a couple of cars every year about this time of year with random alarm incidents which when carefully inspected you find a small web near the sensor and it turns out to be our 8 legged friends.


Richard

 

[Kingpin!]

OK

The other thing that happens at this time of the year is Spiders. We see a couple of cars every year about this time of year with random alarm incidents which when carefully inspected you find a small web near the sensor and it turns out to be our 8 legged friends.


Richard

Richard, it feels like it is the sensor and that the alarm goes off when basically the timer has started the heater.

But, if it is a spider like you say - do you know where the sensor(s) are on a R-Class so I can inspect?

 

[whitenemesis]

Could it also be the hot air being blown out of the heater? The sudden localised change air density triggering the sensor to alarm?

 

[andy27168]

As far as I was aware disabling the motion sensors, does exactly this, the alarm will still operate normally other than this.
Test it, sit in the car lock/arm/disable sensors, then try to open the door.

 

[Kingpin!]

Hi, forum!

I think I have discovered that when my internal heater is on (to warm up the car for a couple of hours so I get ice-free windows in the morning (which in turn is connected to an internal 240VAC outlet on the passenger side)) then the alarm might go on. I also think that if I set the interior motion sensor to off then the alarm stays quiet, at least that is my belief so far.

So, my question is if this behavior is normal - is the interior motion sensor so very sensitive that a heater which just contains a heating element, a blower fan, operating indicator (LED) and standing on the passenger floor might trigger the alarm?

Is it something that can be adjusted (software update even?) or does it indicate some sort of fault/defect?

I would like to have the interior motion sensor set to on by default setting so I don't have to think about activating it all the time when I really need it, even though this option comes up on the display after I turn off the ignition every time.

The car is a 2006 R-Class.

TIA!

Hi forum!

I'm "activating" this old thread once again (after all, I started it! ). Since I discovered the problem that the interior motion sensor activated the alarm every time the heater (standing on the floor on the passenger side) was turned on by timers I've (for years) painstakingly set the interior motion sensor to off using the buttons on the steering wheel every time I've turned off the ignition and left the car, it has worked quite well for years but sometimes I forget and I feel terrible to wake up the neighborhood in the middle of the night.

Now I have another R350 with inbuilt heater (which has positives and negatives) compared to the other R-Class. Thing is that my wife is using the old R-Class now and knowing her and electronics/technical stuff I think this is going to be a "disaster". So, my question is if anybody knows if the interior motion sensor can be set to off like a default setting or if it can be turned off in any other way? I assume that it works the same on GL and ML as the platform is very similar.

Also, I know 100% that it is in fact the heater which triggers the interior motion sensor and the alarm, it's not spiders or flat batteries.

Thankful for any tips!

 

[GLK]

Do you have a button similar to this (can't seem to get an R-class manual online - this is GLS):

Sorry - just read a bit further, and this is the temporary one ... D'oh

 

[Kingpin!]

Thanks for the input but I'm quite sure that I don't have the button you're referring to and like you said it's a temporary one (not "wife"-proof).

I wonder if it's something which can be coded? Maybe you guys with a good knowledge of STAR might know?

 

[richard]

I think it would be possible to electronically remove the option. It will probably take out the anti-tow sensor and the break-glass detectors in the rear most 3 windows. And your insurance company may not appreciate reducing security !

Richard

 

[Kingpin!]

Hmm, maybe a fuse could do the trick?

 

[Uky]

Had the same problem with my old C207. MB workshop could not reduce the sensitivity or disable
that part of the alarm system. Had to perform the button-pressing procedure above every
Winter.

 

[Dec]

It’s probably the sudden warm air turbulence that’s triggering the sensor.

What about a small oil filled heater, on all night, on a very low heat.


See...Mini Oil Filled Radiator | 6 Fin 800W | VonHaus

Dec

 

[Kingpin!]

I just Googled this (the problem that is) and it seems quite common and similar problems with other brands as well. On some car (think it was a Volvo) the sensor was located on the OCP and they simply put tape on it during the winter and all was fine. On Audi it seems possible that the interior motion sensors sensitivity can be adjusted (probably at the workshop), but many brands have the same issues. Suggestions are how you place the heater also since the air travels a bit differently (apparently) which might solve the problem.

Anybody who knows where the sensor is located (is there only one sensor also?) on a R-Class?

BTW, I bought a new "silent" heater this morning to test with, took 2-3 seconds and the alarm went off. I wonder if it's only the air that's affecting the sensor, is it sound as well?

 

[Dec]

Some sensors drop down when the car is locked and close up when the car is unlocked, so the driver doesn’t usually see this event. Tape on the sensor would probably work.


Is the silent heater blowing air?

The sensor would be triggered by heat and movement, so warm air suddenly moving around the cabin would set it off.


Dec

 

[Kingpin!]

Dec, don't have any sensors coming down from the OCP.

Yes, the heater has an heating element and blows that air out in the cabin through a blowing fan.

 

[Stardelta]

I had this problem with the alarm activating on a s204 and went through the ritual of pushing the interior button for deactivating the interior ultrasonic sensors and like you every time I forgot the alarm would sound and then after a few months it stopped going off, so I thought happy days but one day I popped the bonnet to top up the fluids and then shut it and a few minutes after locking the car the alarm started to sound again.
Really fed up I thought perhaps there is a electric switch on the bonnet catch and after some investigating found it, removed it and found no actual fault with the micro switch but readjusted the the flap of metal that pushes against the micro switch so there's slightly more pressure pushing it down and after reassembling have had no more false alarms.
I am presuming that the bonnet switch is deactivated by the button in the cabin that deactivates the interior motion sensors, just a thought for anyone that has the same problem.