Hi Can anyone help?
I have a 2002 model SLK 320 and the indicators will stop working and the bulb failure light comes on at the same time. It will work sometimes but as soon as the bulb failure light comes on then no more indicators!
All bulbs and holders are ok, the hazards work ok, Tried a flasher relay that fits on the right hand side of the engine bay and still no joy!
My arm is getting cold doing hand signals, has any one come across this fault before.
Thanks Hobson.

 

How have you checked the bulbs?
Sure your fuses are OK?
Bulb fail comes on when indicating left or right?
Checked your mirror indicators are OK?

Stuart.

 

Hi
The indicator bulbs etc work fine using hazard lights that shows the bulbs are ok.
When this fault happens the bulb failure light comes on then the indicators do nothing left or right as if I havent even even turned them on.
A merc dealer code read it a while back and it shown nothing also the master tech had not seen this fault before, tried another dealer and they have no idea!
A wiring diagram might help if you know where to get one?
The fault is getting worse it spends more time with no indicators now than having them working.
Cheers hobson..

 

Still sounds like a intermittant bulb or connection. Swap the bulbs out to eliminate. May be the connector on the PC board realy is on in comp box under hood.

Bazzle

 

Interesting.
OK.
The bulbs are OK since the ALL hazard lights work OK. Good test / info.

You state that both the left AND right direction indicators fail to work. Not just one bulb or one side. So the likely cause here is that the LH and RH circuits are not being powered. This would point to the mulrti function switch on the column BUT....why would the bulb warning come on???

Bulb warning is controlled by the PSE Pneumatic Security module in the RH side of the boot under the floor (foam bag with yellow tubes from it) and these are prone to giving a number of complex problems.... like the interior light doesn't work correctly.

In addition it should be understood that the direction indicators are controlled by the Body Electrics module under the bonnet (in the black box at the back of the engine bay). Vehicle electrics are no longer wired/controlled like in the old days. They now use digital control. The Body Electrics black box controls the power source to MANY systems and adds functionality like Soft Fade to the interior light and cause the direction indicators to flash once a second etc. Also responsible for shutting down all power if a door is left open etc. The clever stuff!!

I suspect, but cannot be sure, that your PSE (or some other module) is intermittently causing a "short" across what is known as the CAN. Controller Area Network which is the digital highway between systems.

As a test you could unplug the white multi pin connector on the PSE and see whether this alleviates or at least modifies the symptoms you are experiencing. Of course unplugging this connector will cause your interior light, bulb warning and door locking/security NOT to function. The idea is to determine whether it makes the DI's work again.

From your fault description I would give a 50% confidence in this being the problem But PSE units are moderately expensive so DO NOT swap out until you can turn your problem ON/OFF by disconnecting the connector to which I refer.

I would expect a CAN fault to be stored if the vehicle is put on Star diagnostics (dealer). Using a low cost OBDII engine scanner will not pick up faults on the body/chassis CAN, only the engine CAN.

Are you sure that your security (doors and alarm) and interior light and bulb warning (try removing a bulb in the brake circuit or similar) are working correctly??

Good luck,

Stuart.

 

Good Ideas so far but no joy as yet!
Took out the PSE and tried to disconnect the white plug that looks like it contains the can wiring?? No change to the fault and this was in a fault state at the time. The PSE looks good with no water ever getting in there(bone dry).
Checked Body electrics module and found no poor connections but still possible internal fault?
The rest of the electrical functions of the car are good at all times so a can network fault is unlikely eg can wires shorting out as it would probably cause other system interference also?
Have noticed the temp of car or ambient temp has no effect but the car can be driven approx 20 mins then the bulb failure comes on and no indicators, then drive approx another 20 mins and the failure light goes off and hey indicators are ok!!
This is a challenge to get to the bottom of this fault!
Cheers for the ideas. Any more??
Thanks Hobson

 

Hi,
As you state this is going to be a "difficult" one and careful analysis will be required.

My next question is what happens when the Bulb Warning light comes on?
OK the light comes ON without any action from yourself after 20 mins but IF you try to use the left or right indicators with the bulb fail light ON what happens.
1. Does the bulb fail light remain on?
2. Do the DI's work either Left or Right and if so do all bulbs flash?
3. If so which side works and which doesn.t.

I still suspect my original diagnosis.

4. What happened when you disconnected the White multi plug on the PSE. I don't accept that it made no change. For instance the door locks would stop working. The interior light will stop working on Auto etc etc.
Also I would expect the Bulb Fail warning light to remain OFF since it is triggered from the PSE. If the bulb warning does still come on then this reinforces that something else is initiating the Bulb Fail warning in the Instrument cluster VIA THE CAN (digital highway)
5. You say the PSE was dry. This does not surprise me. The amount of water we are talking about is minute. Condensation may be a better description. The only way of telling if water has been present is if there is a trace of blue salt deposit on the White connector pins on the PSE. You need to look real carefully.

This sort of problem doesn't have a magic bullet solution. It needs VERY careful observation and reporting of what happens.
I'm sure your dealer WOULD find the problem but it may cost you an awful lot of money.

I don't have the advantage of seeing the vehicle in front of me. Nor do I have MB specific diagnostic tools. I can only work from first principles and have to use the data you supply to me so its important that it is as accurate as possible. Maybe your response was 100% accurate in which case I will continue to think about this one.

One last question. Is the problem 100% repeatable. If so what happens if you run with the column multi switch disconnected. (SUBJECT TO SAFETY CONSIDERATIONS) I guess there will be a connector below the steering wheel somewhere.

PM me with your email and I can send you photos (MORE EASILY and better resolution!!) of the connector and CAN wiring. Why can't I embed images? Anyone please!!

I'll try one last time with a less than 63k image.

During Upload I get........./Users/stuart/Desktop/PSEConLowRes is not supported.
Image is PSEConLowRes
Why do i get this problem Mac 10.4.9. JPEG image.
Oh I get it it needs .jpg suffix.
Stupid PC's.

Nirvarna has Mercs and Mac's.

Stuart.

[IMG]local://upfiles/4155/8330D49DBF894EE1BB80886F44D890B1.jpg[/IMG]

 

Hi Stuart.

Had another look at the PSE and yes it is corrosion free.
Tried disconnection of PSE and yes some things stop working as you said (interior light and central locking control)but still bulb failure was on and indicators total dead!!
While doing all these tests the brake warning lights came on (cannot remember the lights but the two that are for brakes and stability control).
Checked lights and hey! things are getting worse, the brake lights have gone and the reverse lights have gone!!
The PSE was all reconnected at this stage and thought that disconnecting it had no impact on my new lamp failures so went for the fuses that supply lights.
Found all lights including the indicators are fed from the fuse panel on the right hand side of dashboard, so started to pull fuses to check for corrosion or loose contacts and the fault status changed and all started to work ok. Then the indicators stopped again so removed the fuse panel/integrated light switch module??( Am I right in calling it that), and cleaned all connections to the unit.
Things worked well for a couple of minutes then the brake lamps went again, so wiggled the wiring and it worked again. Then the indicators went off again so pressed the fuse panel a couple of times and they came back to life.
That was the end of play today. Suspect internal fault in the light switch module or close by loose earth connection or similar. Will take the unit back out tomorrow for a closer inspection.
The fault must lie here as moving the unit stops and starts the fault.
Will update findings on Wednesday, thanks for all the advise and if you still have any thoughts on this update please let me know as its great to have brains to pick!!
Cheers Hobson....

 

Hi,

Looks like you are pretty good at this DIY stuffl..

OK we can leave the PSE (based on you reply) since you have found a source that stop/starts the problem. That is an important step in any diagnosis process.

You mention something which I need to check out.

Does the Bulb Warning illuminate if a lighting fuse blows / intermittant.
I had never considered this before but it would be logical (i.e. lights are not ON) but I had always (maybe erroneously) considered that the monitoring system was purely monitoring volt drop across the bulb.
MAYBE the monitoring circuit looks for current drawn / volt drop across the total circuit rather than just a bulb in which case No Power = Warning Light ON subject to power on for the PSE which does the bulb monitoring, or some CAN problem confusing the PSE.

It would appear that you have located the fault (despite my best efforts to put you off the scent) in that there is a bad connection in the supply to the particular lighting circuit involved.
Now since you have more than one lighting circuit giving trouble eg Tail lights and Brake lights maybe there is a common Power feed/fault.
However this is unlikely since I believe the Tail lights and the Stop lights are supplied TOTALLY separately since one is ignition controlled and the other not.

I didn't think the reverse light was monitored by the Bulb Warning. Maybe this is another learning point.

However both interface with the Lighting switch/module.

I have never taken the lighting switch / fuse box module to bits. When you do find the fault any chance of a picture?

Likely issues are water ingress or more likely relaxation of the pressure on electrical connections due to changes (crystallisation) of the brass connections or a simple break at the termination between wire and contacts.

Let us know exactly what you find.

Good luck.

Stuart

 

What I think is happening is that you are trying to diagnose this as one problem, when there's a high probabilty that they are two unrelated problems. First go through and check every possible outside bulb (side markers, headlights, fog lights, all of them) while it's saying that you have a bulb out.

The turn signals are a pain, I had to replace my turn signal module, it's close to $800 in the U.S. and it's in front of the battery and comes out pretty easily about the size of a small book. I was able to get my from a salvage yard for $125. Similar problem, sometimes they work, sometimes they don't and my kid needed it to work for her driving test so I had to get it fixed.

Lastly, the rear taillight sockets where part of a national recall in the U.S. about a year ago. Check with your MB dealer and see if this is covered.