Have afew electrical problems on clk 320

[Peter James]

Hello everyone this is my first post as I have just joined the forum.
I have just bought a 2005 clk 320 convertible it's a lovely car.
The car has afew electrical issues that I hope someone can help me with.
The main issue is that the seat belt assist for the passenger doesn't work at all ,there is no motor noise but there is resistance when you pull it out manually.
The driver seatbelt assist works fine.
The next issue is that the headlight washer is not working ,no motor noise when the button is pressed and the lights are on, slight dimming of dashboard so I think the switch is OK haven't checked volts on motor.
The last issue is drivers headrest will not go down with the switch, it goes up ok and goes down when the seat is tilted forward and sometimes is does work after the seat has been tilted.I have looked on the forum for the headrest issue and will look at the motor pcb.
Sorry my first post is asking for a lot of information from you guys but any help will be great.

 

[clk320x]

Hello everyone this is my first post as I have just joined the forum.
I have just bought a 2005 clk 320 convertible it's a lovely car.
The car has afew electrical issues that I hope someone can help me with.
The main issue is that the seat belt assist for the passenger doesn't work at all ,there is no motor noise but there is resistance when you pull it out manually.
The driver seatbelt assist works fine.
The next issue is that the headlight washer is not working ,no motor noise when the button is pressed and the lights are on, slight dimming of dashboard so I think the switch is OK haven't checked volts on motor.
The last issue is drivers headrest will not go down with the switch, it goes up ok and goes down when the seat is tilted forward and sometimes is does work after the seat has been tilted.I have looked on the forum for the headrest issue and will look at the motor pcb.
Sorry my first post is asking for a lot of information from you guys but any help will be great.

Hi,

I have been told to sort out the seat you need to run a seat normalisation procedure on STAR.

Mine has the issue on both seats, however havnt had time to sort it yet.

Cheers

 

[Peter James]

Hi,

I have been told to sort out the seat you need to run a seat normalisation procedure on STAR.

Mine has the issue on both seats, however havnt had time to sort it yet.

Cheers

Many thanks for the reply, a friend has the software which I am hoping will check the systems of the car so I will see if it can run the procedure you mentioned. I know the battery was disconnected so maybe a reset on my other issues will help. I will keep everyone updated to any progress.
Peter

 

[Peter James]

Update
Hi today I did some further investigation into the seat belt assist issue.
On a star test the assist worked fine but said the seat belt switch was connected (belt was not plugged in)
On further investigation I found the belt switch was not connected (been cut) and an seat occupancy emulator had been fitted. I have found out the reason for the emulator but don't know if the disconnected belt switch is related.
Any help would be great.

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[Peter James]

I think I've worked it out
With the emulator fitted the system thinks someone is sitting on the seat therefore the seat belt warning would operate so this has been bypassed.
I suppose the only answer is to get a new occupancy sensor mat.



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[Codger49]

Perhaps the PO cut the belt switch leads in a first attempt to stop the seat belt warning. Then found it didn't and found out about the emulator and fitted it.

As a short term measure it may be worth reconnecting the belt switch whilst leaving the emulator in situ. This will probably mean the passenger seat belt butler will operate each time whichever seat is sat on.

The occupancy sensors are not cheap and its a pain to dissemble the seat base to fit it. (Which is why the emulators were produced.)

 

[Peter James]

That sounds like a plan Codger 49
I don't know if the plug end is still in the seat controller but will try to reconnect it and see what happens.
Thanks for the reply.

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[Codger49]

Just a couple of thoughts:

The SRS control unit receives input from the seat belt switch such that it prevents the airbag from firing if the seat belt is not fastened.

The passenger occupancy and child seat recognition sensor unit in the seat give inputs to the SRS control unit such that an unoccupied seat prevents the airbags and tensioner from firing and if a child seat is recognised, the passenger front airbag is not fired.

As far as I know, those emulators only cover the seat occupancy and child seat recognition functions, I think they present a seat occupied signal, (its not just a on -off connection, hence an emulator is required) so the airbags will fire even if the seat is empty. Guess this means a front passenger child seat is a complete no-no with such an emulator fitted.

I think you need to be quite thorough in checking this out, as there may be a risk of your airbags not firing when they should, if the PO has somehow got the c/u to see an unfastened seat belt. I don't know whether the seat belt switch is a simple on-off, if it is maybe just connecting the appropriate leads would fool the c/u.

It also puzzles me why the seat belt extender is not working in normal use, if PO had provided a permament occupied indication, and an unfastened belt indication, I would have thought it would have worked every time. Maybe the canbus trigger for the extender doesn't come from the SRS c/u?

I would have also thought that disconnection of any sensor to the SRS control unit would trigger a SRS warning light in the dash, Have you got this (its an MOT failure), or does it behave normally at ignition switch on? (Unscrupulous owners have been known to remove warning light bulbs).

Guess the next step is to find out what the PO did to the seat belt switch connection?

 

[Peter James]

The more I look into this issue the more concerned I get.
I will not have a child seat in the front but that doesn't mean the next owner won't, also there may be an insurance issue.
As for the SRS lights on the dash they come on and go off as they should.
On the diagnostics the airbag side showed no faults but on the seatbelt assist it said the belt was inserted therefore the assist has no need to operate.
I will try and refit the seatbelt switch and take things from there, maybe later price up a new occupancy sensor and see what is involved with fitting it, I know it's a seat out job and the upholstery has to be removed.

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[Codger49]

Looks as though your passenger airbags would deploy then, as SRS c/u is seeing seat belt as fastened and seat as occupied.

Be sure to identify the seat sensor pad specifically against your VIN, there were changes in this part in late 2004 and also in 2005.

 

[login_user]

Hello everyone this is my first post as I have just joined the forum.
I have just bought a 2005 clk 320 convertible it's a lovely car.
The car has afew electrical issues that I hope someone can help me with.
The main issue is that the seat belt assist for the passenger doesn't work at all ,there is no motor noise but there is resistance when you pull it out manually.
The driver seatbelt assist works fine.
The next issue is that the headlight washer is not working ,no motor noise when the button is pressed and the lights are on, slight dimming of dashboard so I think the switch is OK haven't checked volts on motor.
The last issue is drivers headrest will not go down with the switch, it goes up ok and goes down when the seat is tilted forward and sometimes is does work after the seat has been tilted.I have looked on the forum for the headrest issue and will look at the motor pcb.
Sorry my first post is asking for a lot of information from you guys but any help will be great.

Hey,
The washer motor is a common failure on these, as it's located at the front of the car by the wheel well and collects mud and water. easy to replace.

The headrests always fail, even after reset. You can reset them yourself by raising all the way up and holding the switch in for 10secs, then lower holding the switch in for 10 secs.

Looks like you have the occupancy sensor covered.

 

[Peter James]

Thanks for the info

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[Peter James]

I think I've worked it out
With the emulator fitted the system thinks someone is sitting on the seat therefore the seat belt warning would operate so this has been bypassed.
I suppose the only answer is to get a new occupancy sensor mat.



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Reconnected the seat belt switch today and the seat belt assist now works but I did have to disconnect a seat belt emulator to do this so seat belt alarm comes on unless I clip in the belt when no passenger is present, but at least I now know what everything does.
Thanks to everyone for the information


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[Peter James]

Hello everyone this is my first post as I have just joined the forum.
I have just bought a 2005 clk 320 convertible it's a lovely car.
The car has afew electrical issues that I hope someone can help me with.
The main issue is that the seat belt assist for the passenger doesn't work at all ,there is no motor noise but there is resistance when you pull it out manually.
The driver seatbelt assist works fine.
The next issue is that the headlight washer is not working ,no motor noise when the button is pressed and the lights are on, slight dimming of dashboard so I think the switch is OK haven't checked volts on motor.
The last issue is drivers headrest will not go down with the switch, it goes up ok and goes down when the seat is tilted forward and sometimes is does work after the seat has been tilted.I have looked on the forum for the headrest issue and will look at the motor pcb.
Sorry my first post is asking for a lot of information from you guys but any help will be great.

Update on the headlight washer not working.
First couldn't get the wheel off due to the wheel nuts corroded, anyway got to pump by turning wheel to full left lock and removed a section of the wheel arch protector 3 bolts and 5 push in pins.
Tested the motor on battery and all ok.
Checked volts on 2pin plug to motor and found this had 12v on it all the time.
On connecting the motor the load caused volts to go to zero.
My questions are
When should the headlight washers work e.g. ignition on lights on bonnet closed etc.
How does the circuit work does it go through a relay as this may be faulty and leaking a poor 12v to the motor.
The volts are still there when headlight washer fuse removed.
The battery on the car goes flat when you operate the seats or lights a few times but recovers enough to start the car, I wandering if a current drain to the headlight washer motor would cause this.
Battery has been checked and is ok.
Thanks for any help recieved



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[Codger49]

This text from WIS might be of some help:

Pressing the HCS [SRA] switch (S1s7) in the light switch module
(S1) switches on the HCS [SRA] headlamp cleaning system. The
corresponding input of the front SAM control unit with fuse and
relay module (N10/1), which reads in the HCS [SRA] switch (S1s7),
is switched here to ground. The front SAM control unit with fuse
and relay module (N10/1) connects circuit 30 to the HCS pump
(M5/2). The HCS pump (M5/2) builds pressure up in the washing
water line, which acts against the telescopic nozzle return springs.

This causes the telescopic nozzles to move out and spray water
onto the headlamps. After the on period has elapsed, the pressure
in the washer fluid line drops again and the nozzles move back
into their initial position as a result of the spring force.

As ever, with Mercs, its not very simple.

There's also an internal counter in the front SAM which records windshield washer pump activations, when it reaches 15, it activates the headlamp cleaning system and resets the counter to 0. Counter is also reset to 0 when circuit 15 is off - ignition off.

So you get a automatic headlamp clean for every 15 windshield washes during an ignition on cycle.

15 is the number for cars from 1.6.04 to model year 08, think it reduced (to 7?) after that.

The switching of the HCS pump is carried out by a semiconductor switch within the SAM. Maybe STAR is required to find out exactly what is happening with you HCS system?

 

[Peter James]

Many thanks for the info I think I'll try and find the relay and have a look at that.

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[Codger49]

As I have just added to my post, the HCS is apparently switched in the SAM by a semiconductor switch, not a relay.

 

[Peter James]

Update on the headlight washer not working.
First couldn't get the wheel off due to the wheel nuts corroded, anyway got to pump by turning wheel to full left lock and removed a section of the wheel arch protector 3 bolts and 5 push in pins.
Tested the motor on battery and all ok.
Checked volts on 2pin plug to motor and found this had 12v on it all the time.
On connecting the motor the load caused volts to go to zero.
My questions are
When should the headlight washers work e.g. ignition on lights on bonnet closed etc.
How does the circuit work does it go through a relay as this may be faulty and leaking a poor 12v to the motor.
The volts are still there when headlight washer fuse removed.
The battery on the car goes flat when you operate the seats or lights a few times but recovers enough to start the car, I wandering if a current drain to the headlight washer motor would cause this.
Battery has been checked and is ok.
Thanks for any help recieved



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Further update on headlight washers.
I've been a complete tool on this one.
Spent a good 2 hours on this testing pump,getting 12volts all the time etc
Only to find I've been checking the windscreen pump and not the headlight pump which I completely missed as it was white against the white water filler.
Changed pump now both washers extend water comes out of one but the other seems blocked and there appears to be a leak as a lot of water appears from under the car. This is probably a perished tube or something straight forward. Anyway at least I know where both pumps are now.

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