w202 slow flashing red light in rear view mirror surround

[PhilPat]

Hi Guys,

Have owned my W202 1997 pre facelift C180 since it was a year old and love it - only recently discovered this forum and have found it to be a great source of info!

Just recently, immediately after start up, the red light in the base of the rear view mirror has started to slowly flash (i have the model with the red and green lights at the base of the mirror and flip key) - at appprox 10 second intervals for about a minute or so. The car is otherwise fine and starts/ drives normally - on locking, the red light flashes and on unlocking, the green light flashes - all as per normal

Have search the site and looked at my handbook but can't find any direct refence to this slow red light only flashing. Has anyone else encountered this or know what it means?

Many thanks in advance

Phil

 

[KillerHERTZ]

It means the keyfob batteries are on their way out

Zee Germans have thought of everything...

 

[PhilPat]

Thanks for the quick reply killerHERTZ!

I had thought that the keyfob battery warning was when both the red and the green flash together at a frequency of every couple of seconds? Have encounterd that before about a year ago and new batteries cured it

In any case, I'll change the batteries as a first step and see what happens

Phil

 

[KillerHERTZ]

IIRC, its the immobiliser in the ignition barrel telling you that the batteries are low, causing just the red light.

Where as the green/red flashing when you lock/unlock it is the reciver is telling you its lower power (I hope this makes sense)

 

[Dec]

I haven’t ever heard of a slow flash at 10-second intervals before, my understanding is,
Red light flashes = locking and immobilizer arms.
Green light flashes = unlocking and immobilizer disarms.
Red and Green flashing simultaneously = weak batteries in fob.
Red and Green flashing alternately when key turned to position 2 = immobilizer hasn’t disarmed which would be the result if batteries were weak or dead.

Dec
Edit, Just in addition to the above, that is how it is on my 1994 car a 1997 may well be a different set up.

 

[BTB 500]

On my 1997 SL, low fob battery is red & green flashing together.

 

[PhilPat]

Thanks guys - much appreciated

Dec/BTB - that's exactly my understanding, this slow flashing red light only is a completely new one on me

KillerHERTZ - thanks for the clarification. essentially you reckon its another way of indicating that my keyfob batts are low then? will try with a spare key and let you know how i get on with it. I also have the red plastic alarm fob so will pop that into the slot in the glovebox & see if it makes any difference - have always been a bit vague on exactly what that does!

I suppose i was a bit worried that this slow flashing red was an indicator of some kind of immobilizer/alarm fault

All the best

Phil

 

[PhilPat]

Update - Well, have fitted new batteries to the block key and nothing has changed, am still getting the slow flashing red light in the rear view mirror surround for a couple of minutes after start up.

Does anyone know what might cause this and what i can check next? this one has got me stumped!

Many thanks in advance

Phil

 

[Dec]

Phil, can you turn off the alarm system and see if the flashing Red LED stops doing what it is doing, lock up the car and wait a few minutes and try again to see what happens.

Dec

 

[PhilPat]

Thanks Dec - i'm unsure how to turn the alarm off. I have a red alarm fob, (measuing about 1.5 inches by half a inch) which goes into a slot in the glove box but i am unsure exactly what this does or indeed if there is a way of turning off the alarm. I don't need this red plastic fob for the normal operation of the car.

To recap, the car is w202 1997 pre facelift with the block flip key and red/ green lights in the the rear view mirror and no lights in the door handle

P

 

[Dec]

That’s too modern for me, someone will be more familiar with the way to turn off alarm on your car and post how it is done.

At a wild guess that red thing you mention might be what you do, plug it in and see what happens.

Dec

 

[PhilPat]

Thanks Dec - i've never had to use the red fob so far, it's function isn't mentioned in the owners manual at all. I'll give it a try through. I presumed is was used to reset the alarm?! Much prefer the older Merc Scorpion alarms with the cylindrical key that you could use to turn the alarm off, much simpler!

P

 

[andy27168]

Hi,
Some info straight from the MB book re; this type of alarm
There is a small separate very thin book just on the alarm, there is no pt. no. on this book but it says that,
The black touch key is for disarming the alarm system, in the event of the infra-red key is not functioning.
The red touch key is used by the dealer for programming new black touch keys and diagnostic purposes. This key should be kept in a safe place and not in the vehicle.
There should also be a "Credit Card" key as well, which is the spare key for the vehicle and will lock/unlock the vehicle and will arm/disarm the system, but will not activate the comfort locking (closing of the windows etc.)
This alarm system is quoted on the Thatcham list as a catagory 1 system, and is referred to as MBSS2a (Mercedes-Benz Security System), and was fitted too the 202, 210, 129, 170, and the 140 (CL & S Class).
Hoped this has helped.

 

[PhilPat]

Thanks Andy, very helpful & useful info, much appreciated - i don't have that booklet but I do have the credit card key and the red alarm fob, i don't have any black ones though - will see if i can get hold of some to program - is there any detail on how the programming of the black fobs is done?

P

 

[salukigb]

W202 RVM single red flashing light

Hi,
I noticed the thread about RVM red light and I have exactly the same "problem". Did you ever sort the problem and if so what did you do?/
Thanks

 

[Grahamcol]

Not certain about this but I think my C200 did something similar when the car battery was on its way out !

 

[bennesspipers]

If your alarms the same as mine,pull back the rubber boot & easily pull out the cable block from the back of it. These alarms are a pain.

 

[Chris19143]

I have the same problem. Did you ever manage to find a solution? Chris

 

[poormansporsche]

My car did this and never caused a problem until I sold the car and then the alarm wouldn't turn off ! The slow flashing red light may be a sign that the rechargeable battery hard wired in the siren is on its way out and is not replaceable. We just disconnected the alarm in the end