W163 Remote locking u/s and no security light?

[miggit]

Hi, I've been struck by electrical gremlins... again
The remote key stopped working... so I changed the batteries, and still nothing
So there I was, sat in the car feeling a little miffed, as it was obviously going to be a little more involved, and I noticed that the blinking light on the dash wasn't blinking anymore and the indicators have stopped flashing.. Alarm fault?? Should I be worried??
I can't find any info on the web and I'm getting the feeling that the security system is karput
Can anyone offer a possible fix that doesn't involve massive amounts of dosh?
Failing that has anyone added an aftermarket remote to the C/L system to get around this fault....
The car will totally unlock with the key, but wont lock... so I have to use the button on the console to lock all the doors except the drivers, and then use the key on that door.... However if the drivers door is shut the whole car will lock with the console button, so I'm hopeful that a Ping Pong remote C/L kit can be added to the console button without too many tears... But I'd rather restore the original system as it will give me an alarm again

 

[Dec]

If the alarm is the original, then its 18 years old and likely to be faulty so best to unplug it to see what transpires.

Before using the button on the console, open the drivers door then lock the other doors with the button on the console, then shut the drivers door and lock with the key.

Try pointing the remote a few mm from the sensor on the door handle to see if that will lock/unlock the car.

Check any fuses relating to alarm or central locking.

Edit;
Useful thread relating to the alarm, here… ML270 (w163) 2003 alarm unit



Dec

 

[miggit]

Hi, yes the lock all doors with drivers open and use key on drivers is what I'm having to do, just a tad annoying as the key will totally unlock the car, but only lock the drivers door!

As far as the alarm goes.. I could have the oldest working (until last week) example... or it could have gone up the pictures and the replacement has just expired! So the big question is... when the rechargeables in the alarm sounder give up the ghost, does it stop the dash security / armed light from working? as well as fubaring the central locking... And does anyone know where it little gritter can be found.... I know where it is on the facelift cars.. only mine isn't a facelift

 

[Dec]

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The video above shows how to remove the wiper mechanism & motor, the alarm siren is located under the wiper mechanism & motor, if you intend to replace the alarm siren then its best you first obtain an alarm siren before you start removing the wiper mechanism & motor so you can fit it straight away.

Note; the car in the above video is Canadian and doesn’t have the alarm siren under the wipers mechanism but the UK version does.

The blinking Red alarm light indicates the alarm is armed, however, if the central locking is not working from the remote fob then the alarm will not be armed, so, there will be no blinking Red light.

Did you try locking with the remote fob just 2 mm from the door handle sensor and did you check fuses?


Dec

 

[miggit]

Right the first thing that I can report on is that it's freezing out there!!
Key fob almost touching the lock on drivers door... nothing!!
Fuses, I checked them the other day and couldn't find anything blown under the bonnet.... however I also couldn't find which fuse I need to be checking as the hand book said look at the fuse box lid, and the fuse box lid was about as much use as a chocolate fire guard! So I had a good root about, but couldn't find anything chard or corroded.... Not sure if there is any other fuse boxes in the car... the hand book only said about the under bonnet lot!

 

[Dec]

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[miggit]

Well that's something to look for when it's a bit warmer!! ( the boot is full!)

One thing that's puzzling me is you said the blinking light is only on with the alarm... my blinking light used to come on all the time except when the engine was running.... in other words I had the blinking light when the car was open and the engine was off, but the radio was on... key in acc position!

And the other thing is I have flip keys that don't have an indicator on them to say if they are working or not... but it didn't work with the old batteries and still doesn't work with new batteries!

 

[Dec]

Sorry, I forgot you have the flip out key, you can test it through a smart phone camera.


Whe you unlock the car with the remote fob the alarm should disarm and the blinking Red light should go out, if it stayed on when the remote was in working order then the alarm is faulty.


Test the key as in above picture through a digital camera.

Do you have a working spare remote fob?


Dec

 

[miggit]

I think we are talking about different keys... mine is a 3 button flip key that is RF, not IR.. it looks like this

I have discovered that they can sometimes need to be resynked when the batteries are changed, so I'll give that a go tomorrow... but I wont get my hopes up too much!!

 

[Dec]

That's the later one, there doesn't seem to be any way of testing if there is no test light.
Re-sync will be worth a try.

Dec

 

[miggit]

Well the resync was a waist of time, as suspected it's going to be more expensive
So if I'm understanding what I've read, if the batteries fail in the alarm siren it takes the whole system down with it.... Bloody stupid design that one....
I have also seen that some peeps have had success by replacing the batteries and refitting the old siren.... I'm now wondering if there is a way to tell other than forking out a shed load of dosh and then discovering it's a AAM instead..... I have a radio that turns itself on and off randomly, and sometimes wipes it's memory for good measure... just haven't so far been able to determine if it's the car or a dodgy connection in the head unit itself... no matter how I wiggle the wires with the radio out I can't get it to fail

Wondering if it's worth just getting a s/h siren and rebuilding it with new batteries, rather than the £100+ that a new one costs, just in case it's not that...

 

[Dec]

The alarm siren has a circuit board inside it; if the components on the board become damaged / corrupt then replacing the alarm siren batteries won’t help.

If some, but not all the components on the siren circuit board fail then you start to get odd symptoms like your flashing hazards OR the alarm going off in the middle of the night, OR the alarm going off with just hazards flashing but no sound from the siren OR the Red alarm light staying on when the key is in the ignition.

These are the symptoms of a faulty alarm siren, very common at the age of your vehicle.

You could unplug the alarm siren and then disconnect the car battery earth / ground lead for 10 minutes to see if that resets anything then reconnect the earth / ground. Unplugging the siren won’t cost anything; the car will work fine without a siren.

This is just an opinion, that it’s a faulty alarm siren, it could be something else, you may need to have it hooked up to diagnostics, not much else you can do other than check fuses.

Joderest bought a used siren for £30 and it turned out ok, see… ML270 (w163) 2003 alarm unit.

See also… mercedes alarm siren circuit board - Google Search

Dec

 

[Joderest]

What!!!!!, how dare you, 30 quid, never, it was 15 quid!!!!!!!.
Anyway, I suspect you may well have an AAM fault, or it could be alarm unit. I think you should check but I think the alarm location on pre face lifts is under one of the wheel arch liners, do not know which side. I think face lift was under wipers like mine was as car a 2003 MY.
My alarm works as it should now, the old one did not sound and did not give three flashes on lock.
I have read somewhere that a fault like you discribe turned out to be the AAM ecu.
I think I would seek a code read, then decide as AAM has to be coded on star

 

[Dec]

Now I remember, it was worth £30 and you got it for £15.

Dec

 

[Petrol Pete]

Find the siren, disconnect it and see what happens. I have seen the same type of gremlins on a W203 C class, disconnecting the siren worked. The siren was beyond repair and has not been replaced, who needs it ? as for adding an aftermarket alarm , that will be more hassle than its worth. How many times has your 18 year old car been broken into while in your ownership ?

 

[miggit]

Right so unplugging the siren might fix it, but it shouldn't make matters worse?

And where did you get fitting a new alarm from?? I would in no way attempt to fit another alarm to a car that has a fully integrated system.. that is just asking for tears.. What I was intending to fit is a new remote key to the central locking system, I fitted one to my Range Rover.... Which was made in 1988, came with an alarm fob, factory fitted LUCAS alarm Which was/ is dormant and has been left well alone.... One wouldn't want to stir up a Hornets nest by operating the fob!!

So I left it well alone and fitted a remote system to the central locking... that proved to be a mission and ended up with a slave actuator as the ****-o-mamy 4 wire system refused to be integrated..... the only God send is that I can sleep well at night safe in the knowledge that there are no ECU's in that car!

The whole add on system was around a tenner, and came with flip keys!! The standard fob type systems are cheaper and could prove to be a cheaper and easier way to lock the car... I have only got 1 key, and I cringe everytime I turn it in the lock, either way an extra key or new AAM is going to be in the many hundreds of pounds to sort... Quite frankly the car isn't worth that expenditure as it's getting near the quarter of a million mile mark and starting to get a wee bit tired!!

 

[Dec]

Relays K15-K20-K23-K24 central locking

Fuse 42 central locking

http://www.mercedesmedic.com/1998-2005-benz-ml320-ml350-ml500-fuse-box-location-diagram/

Dec