I don't know the part#but.
I think the belt relay is located under the front seat.
Regards.
aam.

 

Thanks for the reply.
Originally I did check underneath the seats but didn't notice an appropriate spot. I'll check again.

Thanks for the help. It's greatly appreciated.

 

What you have is a backrest "Safety Package" module. There is one located under each seat (picture). These monitor the latched/unlatched status of the backrests through microswitches on the latches and will sound an audible alarm if the car is in motion with a backrest unlatched.

 

After finding the correct bolts, removal of the bottom section of the seats was quite simple. A little too simply for a Benz. The seat belt relay was under the driver's side seat. I popped the relay in it's spot, started the car and the seat belt light flashed and then went away.

Thanks alot for all your help.

 

Hi!

I too have this annoying situation where the seat belt light is always on!
I had this issue intermittently for quite some time but anytime I used to turn the ignition off and then on the light used to switch off immediately.
Until 5 days ago I removed the seat and back cushions off to repkace the backrest back cover and when I reassembled everything the seat belt light stayed forever on!
Of course it blinks 4 times after firing the engine but since then it would stay permanently on!
I tried to figure out what was the cause of it. But didn't notice anything wrong rather than the thick black/yellow electric wire with flat red plug that has been obviously split into 2 by the previous owner. I too noticed that it has been reconnected (like for troubleshooting) with black electric tape. May be to connect the blue and brown internal wires together...
Oh and there is no alarm sound coming out from the blue micro switch on the seat latch...
Could it be coming from this wire or the seat belt relay ?? I don't see anything wrong cause nothing has been damaged from my side ..

 

Bob you are there??

 

Each backrest has a microswitch on each of its two latches that verify the backrest is locked in place (S51/1, S51/2, S51/3, S51/4). The switches are wired to the "Safety Package" modules N32/7 and N32/8.

I suggest you refer to the attached schematic to check if all 4 microswitches are signaling they are closed. You access the N55 connectors and the modules under each bottom seat cushion as shown in the post from 2008.

 

Bob I don't know exactly how to check the connectors for close signal. Can you explain please?
Btw, I checked the passenger seat and the switches look nice and smooth. I sprayed some contact cleaner on them too.
Do you know what is the function of the yellow/black wire?

 

I would remove each Safety module and identify the sockets #5 and #8 of the connector to which it was plugged in. You do that either explicitly either by finding the sockets numbered or identifying them by the color of the associated wires (see schematic). If the seatback switches are closed, then you would measure c. zero ohms resistance between the two sockets.

I don't see a yellow/black wire on the schematic...

 

Ok Bob!
I will manage to remove the plugs and test the resistance of each micro switch.
Now let's suppose one of them is out of specs; the remedy would be to replace it?
Is this an easy job or does it require some advanced skills??
Thnxxx

 

Hey Bob!
I tried to measure the resistance as you described but I'm frustrated cause I couldn't get to remove the safety package relay from its plug!
Man is it so stuck in place... Is there a way to remove it safely?? Like a lock somewhere around or do I have to continue pulling it up?
I'm afraid to break this precious crappy plastic housing or to separate the wires from the plug! Any advise?

Regards,

 

You can test the switches by removing the 2-pole electrical connectors A1 and A2. They are located next to the Safety module.

If you don't get a low-resistance reading from both connectors, then I presume you'd need to gain access to the switches to investigate.

 

I was finally able to measure the resistance of the switches at the A1&A2 plugs and guess what?? They are within specs: 1.5 / 1.8 ohms only!
Bob, that may lead us to which direction??

 

If you look at the schematic you'll see that the cluster reads a voltage which comes from the pin #3 of each Safety module. I would want to know what that voltage is or manipulate it to see how the instrument cluster warning indicator responds.

For that you want to remove one or both Safety modules. I don't suppose it is too difficult, because I have a pair of them which I removed from a parts car.

You may find the path of least resistance to an acceptable solution is to simply remove the warning indicator's bulb from the cluster.

 

I understand very well that the easiest thing to do is to remove the bulb from the cluster yet if a repair is possible I would like to try it...
What if I just replace the safety module? do you think it would do the trick Bob?
I can find a spare module from a friend's parted SL... now that we know the switches are ok...
And for the peace of mind I can swapp my current cluster with another one to eliminate the possibility of a corrupted cluster... that would leave us with the module alone, right??

 

Swapping-in two known-good Safety modules from another car and/or a cluster would be helpful. It seems to me the malfunction you are experiencing is very likely with one of those components, though it could be wiring too.

 

Hi!

Bob, I swapped in the modules to no avail...
Then I connected a known working cluster and man guess what??? The seat belt lamp blinked as normal then turned off!!! I couldn't believe it so I turned the engine on and off a couple of times and all was fine...
I really am amazed!
What could have went wrong in my cluster so the lamp is all the time on?!!
Anyways, now I feel more relax but I need to know if a repair(a diy fix perhaps?) Is possible??
Thanks a lot!

 

I have no notion for how difficult it would be to make this cluster repair. Possibly you could contact MBCluster and receive some guidance.

Since you are determined to have the warning bulb functional, I presume it's worth your while to remove the cluster and have a look at its circuit board. By way of examination I would try to trace the signal path from the warning bulb back to the device which controls it and perhaps further still all the way back to the connector pin which receives the signal from the Safety modules. In this process you might spot a questionable solder connection to be touched-up, a component which is burned or shows other obvious damage, or a transistor to check.

 

Ok Bob!

Will definetly try to follow the trail of the bulb to the source. But one question: which pin # is linked to the seat belt warning lamp on the cluster plug??

 

The warning lamp signal comes from socket #7 of connector 2. You can discern which that is by looking at the attached diagram of the sockets, and from that you can determine which pin on the socket board provides a signal for the warning lamp.