Outside door lock lights stay on

[LeaUK]

I've been following this article (having no problems of my own) with interest, and now, yes you got it, I can now join in with my personal experience!

I've read every post about remote locking I can find, but there just doesn't seem to be any definitive answers - so I posted a quick question on the Tech Help forum:

On rare occasions my remote fails to unlock the car, this applies to any sensor. (Not quite true as recently I've noticed that the majority of remote lock/unlock failures appear when using the driver’s door sensor)

Following this failure, and by using the key in the driver’s door (not tested others) the car unlocks fine. Subsequently, by locking the car, the red light stays on permanently for around 20 seconds - this I'm sure is a warning! [I] (recently, instead of a constant illumination I get a flashing which lasts around 20/30 seconds) [I] The remote often operates fine afterwards, but not upon every failure.

Last night I happened to notice that the normal sequence of flashing lights, upon lock and unlock, (10 short pulses of green / 5 short pulses of red) had changed and that pulse 4, of red, was of longer duration.

Being an electronic eng. I expect MB use pulse codes to indicate failure modes - does anyone know how to interpret these or has anyone any recommendations for cure?

Maybe these codes are accessible from the 9 pin diagnostic connector (I can't find the 38 pin and so I don't think my car has one) - if so, can I connect an LED to one of the pins? Does anyone have the full fault code listing too?

In response I received a couple of pointers but again nothing definitive. So, did you guys ever resolve your issues?

I'm trying to reproduce the error on request (intermittant faults are always the worst!) and in doing so have discovered that the car will not lock using the remote if you leave a key in the ignition. This makes sense, as you wouldn't want to arm the car with the key left in there, so that ‘might’ be a little clue! But, I cannot reproduce my specific problem. It’s just intermittent!!

Due to the tight integration between the Infrared Remote Central Locking (IRCL) unit and the Anti-Theft Alarm (ATA) module it's difficult to know where to begin, but in my experience it’s always an electromechanical device that’s to blame.

For me, the drivers door fails more regularly than the other sensors, so perhaps I disturbed it when I fitted a new electric window motor!??

I’ll let you all know if I find out anything more of interest.


Cheers

Lea

[CDNC36AMG]

Learoy....haven't taken mine in yet as its only an annoyance. As I have to get my radio checked shortly I will be.

That said after reading this thread I have concluded the following action is warranted....

First, check the fuses. I note that I have never set off my alarm in any way & won't be surprised if its the alarm system fuse.

Second, clean & tighten all connections related to the alarm & door systems.

My bet is that one or the other fixes the problem. I really doubt its a sensor as they each work in different ways one day to the next. Not consistent to having one bad sensor.

Yes, on mine the drivers door is the worst culprit.

[Momo]

The problem has come back for me. During my last service, the mechanic cleaned the alarm box connector, which seems to have helped. However, the right side sensor does not work. I suppose I should fix it before complaining too much. While I can no doubt buy the part, is any particular expertise or special tool required to install it and program it?

At the moment, the problem continues to be intermittent, though the light stayed on through the whole of last weekend. Normally it goes out after a few minutes or an hour.

Momo

[LeaUK]

Interesting. That's all three of us with individual 'intermittent' door sensors!

I agree that it's not consistent - the IR sensor would either fail or function - very rarely in electronics is their a halfway house. In my experience it's almost always an electromechanical device that's misaligned or purely failed.

If only I could reproduce the problem we'd be half way there. If I find out anything I'll let you both know.


Lea

[r129 300sl]

Hi,

My system is working fine after about a year. The only thing that was done was to clean the connectors in the boot as opposed to the main dealers' suggestion to replace all 3 receivers (£500).

Regards

[CDNC36AMG]

Learoy, here's my situation.

Remote works on driver door about 30% of the time, the key rarely.

Remote works on trunk about 95% of time....both green & red flash. When the trunk doesn't work key in pass. door is the only way and the red lights stay on for 10 seconds or so.

Remote works on passenger door about 50% but key always works.

Sometimes gets better sometimes worse. I agree, sensor replacement seems an unlikely fix except that connections would get cleaned. Hence my course of action.

[LeaUK]

With the comments made by pep and Gilly yesterday see thread I've finally found the answer for my car.

There I was, oscilloscope, DVM and various other electronic diag tools in the boot ready for some serious debug and all that it took was my bare hands

It's definitely the sensors. As pep did, I too tried the light test - with perfect results.

If your car suffers similar intermittent problems try this:

1. Does your remote work at night, or at least perform more reliably? If so we're half way there.

2. During the day when the remote locking is intermittent (or as in my case the drivers door just refuses to operate at all), cup your hands around the offending sensor such that you block all stray sunlight entering. Now point the IR remote at the sensor.
Voilà!

3. If your CL still refuses to operate, move the remote closer to the sensor and make sure NO stray sunlight hits the sensor.

4. During the night when your CL is working, shine a torch on to the IR sensor surface - this doesn't have to be a powerful torch - voilà, it stops working again, just like daytime!

What I suspect is happening is that over time the surface of the IR receiver becomes lightly scratched by your thumb. This mist of fine scratches refracts sunlight hitting the surface and the sensor cannot decipher the real IR signal sent from the remote, amonst the sunlight 'noise'.

This hypotheses also ties in with why driver's doors seem more intermittent and the boot the most reliable and why MB changed the IR receiver to inside the car.

Yesterday I stripped the door panel down (again) - to remove the IR sensors looks like a nightmare, so I'm off to review what AlldayaDIY have to say.

Hope this helps out the other members here with similar problems - why not let me know how you got on with the above tests

Lea