W211 2004 wiring in boot

[RSS]

Two questions:-

1st
I need to pick up a permanent 12v feed for the trailer bypass relay, I have all the panels off in the boot and can see a large 12v distribution cable panel on the RH side of the spare wheel well. What I'd prefer to do is use one of the spare fuse slots from the fuse panel next to the DVD cage. There are a few spare fuse slots but has anyone fitted this before, if so where did you pick the power up from, there are sockets at the back so assume with the correct fuse fitted I should (I hope) be able to pick up power with the right connector in the right slot.

2nd
Anyone have the wiring code for the rear lights, the towbar kit I have is wrong referring to wires that are not there. I'll give the supplier a call tomorrow as well but just in case they are wrong again.

 

[RSS]

This fuse panel I referred to is the SAM unit in the boot, where can I pick up a permanent 12v from it and where can I get the connector from?

 

[Alps]

main dealer will have access to the part number for you.

 

[RSS]

Speaking to MB dealer they didn't have access to the details for the SAM unit in the boot and said that picking power up from that unit is tricky as a lot of the connectors are simply signals.

Shame really as there are plenty of spare fuse slots and it would have made it look neat.

If anyone has an old one of these that I can pull apart to look at that would help or looks like I'll have to connect back to the battery distribution panel.

 

[Diesel Benz]

Speaking to MB dealer they didn't have access to the details for the SAM unit in the boot and said that picking power up from that unit is tricky as a lot of the connectors are simply signals.

Shame really as there are plenty of spare fuse slots and it would have made it look neat.

If anyone has an old one of these that I can pull apart to look at that would help or looks like I'll have to connect back to the battery distribution panel.

But they would have WIS and could find the wiring diagram from there. The rear SAM has a lot of signals but I don't think any spare fuse slot would be a signal, the question is more if the fuse provides continuous power or switched. I understand that you would not be looking for a big fuse, something that can drive a relay? Any spare would be able to do that as long as it has permanent power if that is what you are after.

I did not check but would one of the trailer hitch fuses do for you or do you have those already in use?

 

[RSS]

The fuse intended for the trailer would be perfect, this bypass relay powers the trailer lights and I would think with indicators, side and brake lights on at the same time there could not be more than 7 amps being supplied.

I can't find out any information on the SAM, if I could fit a suitable fuse for a vacant slot (10a would be perfect) and where I can pick the fused supply off from it would be great.

There are plenty of numbered connectors on the SAM, some I can see are light weight so these are probably signal connections but others look like suitable pick ups for the bypass relay power I need. It needs to be a permanent 12v.

I've even tried to locate an old broken SAM that I can take apart to trace a suitable supply.

 

[Diesel Benz]

The fuse intended for the trailer would be perfect, this bypass relay powers the trailer lights and I would think with indicators, side and brake lights on at the same time there could not be more than 7 amps being supplied.

I can't find out any information on the SAM, if I could fit a suitable fuse for a vacant slot (10a would be perfect) and where I can pick the fused supply off from it would be great.

There are plenty of numbered connectors on the SAM, some I can see are light weight so these are probably signal connections but others look like suitable pick ups for the bypass relay power I need. It needs to be a permanent 12v.

I've even tried to locate an old broken SAM that I can take apart to trace a suitable supply.

From the wiring diagram it looks like there are several options for a circuit 30 (permanent power) source. You would just have to decide which fuse to use and then figure out the fuse holder part number. These are mechanically coded, basically one only fits into one specific position (at least not to any of the nearby slots).

The fuse holder simply slides into its position and locks itself.

 

[RSS]

From the wiring diagram it looks like there are several options for a circuit 30 (permanent power) source. You would just have to decide which fuse to use and then figure out the fuse holder part number. These are mechanically coded, basically one only fits into one specific position (at least not to any of the nearby slots).

The fuse holder simply slides into its position and locks itself.

Thanks for the reply, spare fuse locations are 12, 7 and 5. I don't know what the other fuses do, don't have a table for them but if one of the spare ones is allocated for a trailer then perfect. It needs to be without a relay as there is no point running a relay 24/7 off the battery, minimal drain but just not needed.
If all else fails then I'll have to look at picking up a feed from the 12v distribution panel in the spare wheel well and run through an inline fuse.
If you have the wiring chart can you confirm the wire colours to the rear lights, the towbar company said they had two options for the wires:-
Option 1
LH Ind - Black/White
RH Ind - Black/Green
Brake - Green/Yellow
RH Side - Black/Red
LH Side - Black/Red
Fog - Blue/Green
When I couldn't see RH Side Black/Red or Brake Green/Yellow wire they gave me these codes.
Option 2
LH Ind - Green/Blue
RH Ind - Blue/Black
Brake - Black/Red
RH Side - Grey/Red
LH Side - Grey/Black
Fog - Grey/Red
Not had a chance to check these on my car yet.

 

[RSS]

Diesel Benz

Did you manage to find out any wiring information on the SAM with those spare slots that I have.

 

[RSS]

I've fitted the bypass relay now, in the end I dropped off one of the rear lights to confirm the wiring, interesting....

All the lamps in the cluster are the same just driven at different voltages for the required brightness. Tail and indicator lamps are paired with a common return for all the cluster lamps. I assume this is so that if one blows you still have the other one working.

I took some pictures of the relay fitted and the loom I opened to get to the wires for both sides. Couldn't find any information on picking up a permanent feed from the rear SAM so ended up fitting a separate fuse holder and connecting straight into the 12v distribution panel in the spare wheel well.

For the final connection I dropped off the negative post from the battery in the boot. I read about various issues that people have had with disconnecting the battery but as this was only for 5 minutes I figured it would be OK.

I can report that apart from needing to save the memory seat setting and resetting the drivers window up and down it went by without issue. The other windows were fine just the drivers one needed it to get the one touch close working again.

I've just ordered the additional strengthener bars for the boot, they are over the top for the small trailer I intend to use but in case I ever tow anything bigger I didn't want to go through the hassle of taking all the boot panels out again.
P/N A211 639 0143 (£7.85) and A211 639 0443 (£10.60). Neither come with the bolts required (M6 x 12), they were 95p each from MB....!
I simply got all 8 from my local tool shop for a total of £1.30, result

 

[Diesel Benz]

Thanks for the reply, spare fuse locations are 12, 7 and 5. I don't know what the other fuses do, don't have a table for them but if one of the spare ones is allocated for a trailer then perfect. It needs to be without a relay as there is no point running a relay 24/7 off the battery, minimal drain but just not needed.
If all else fails then I'll have to look at picking up a feed from the 12v distribution panel in the spare wheel well and run through an inline fuse.
If you have the wiring chart can you confirm the wire colours to the rear lights, the towbar company said they had two options for the wires:-
Option 1
LH Ind - Black/White
RH Ind - Black/Green
Brake - Green/Yellow
RH Side - Black/Red
LH Side - Black/Red
Fog - Blue/Green
When I couldn't see RH Side Black/Red or Brake Green/Yellow wire they gave me these codes.
Option 2
LH Ind - Green/Blue
RH Ind - Blue/Black
Brake - Black/Red
RH Side - Grey/Red
LH Side - Grey/Black
Fog - Grey/Red
Not had a chance to check these on my car yet.

View attachment 19382

Hi, sorry but for some reason I have missed this thread completely. You really should have sent a reminder via PM (while posting on the forum of course too, allowing others to reply).

It is too late now but perhaps someone else needs the info in the future. Fuse #5 is a circuit 30 source, assigned for a spare relay 2, N10/2kC) while fuse #7 and #12 are circuit 15R fed.

The wiring option 2 seems correct except that LH indicator should be Green/Black. Left stop lamp should be Black/Red but the right stop lamp should be Black/Yellow.

The inner left tail lamp/fog lamp is Green/Blue, the inner right tail lamp/fog lamp is Grey/Green.

I would prefer everyone reading this directly from the diagram, so easy to make mistakes when reading the diagram.

But are you going to tap wires to the rear lights wiring harness? Why not use a proper tow bar wiring harness set?

I'm reading this for a LHD sedan model but the rear wiring should be the same for RHD cars too.

 

[RSS]

Thanks for the reply, this was one of those jobs that I was trying to get completed before we went on holiday and just ran out of time. I did look at the complete harness for the towbar but this required connection to the STAR system afterwards to set up and what with the harness costing £120 plus the trip to the MB dealer it was getting too much just to simply tow a small trailer. In the end the bypass relay looked the best bet.

Connections I used were:-
LH Ind - Black/White
RH Ind - Black/Green
Brake - Black/Red
RH Side - Grey/Red
LH Side - Grey/Black

The trailer does not use reversing or fog lights and there are no connections for them either with the cable I had. Tested them and all working, one thing I never noticed before is that there is only one rear fog light on the RH side. Nothing reported on the dash to say a lamp is not working so assume that that is normal.

 

[RSS]

Pictures for the towbar wiring as follows:-

I prefer to solder the wires for the best connection. Use heat shrink to hold two of the wires together and then wind some thin tinned copper wire round the third one to both hold it in place and help the solder to flow. Cut the ends of the tinned copper wire off when you have wound it round a few times and solder.


Here they all are finished.


Then I wound the MB loom cover back on and held in place with two wire wraps to keep it all in place.


I only seem to be able to attach 3 pictures so will try to post the other pictures in the next post.

 

[RSS]

Bypass relay held in place on the DVD cage, I mounted it on a small piece of cardboard to keep the click of the relay to a minimum.


This is where I connected into the 12v supply. The fuse holder was one I bought at Maplins that takes the standard car blade fuses.


This is the feed run as much as possible alongside the fitted cable. The two earth wires I put into a ring terminal and found a spare earth post complete with nut. You can also see the trailer cable running along the base of the boot, this will be covered and held in place by the plastic jack holder that I removed.

 

[Diesel Benz]

This is where I connected into the 12v supply. The fuse holder was one I bought at Maplins that takes the standard car blade fuses.

So you decided to feed power from the rear prefuse box. This is quite OK when you did insert a fuse next to the connecting point.

You could have used one of the spare positions next to the pink and blue fuse holders, all are circuit 30 fuses anyway. The Maplins fuse holder must have been a bit less expensive and a lot easier to get hold of.

Overall nice and clean installation.

 

[RSS]

Thanks for the reply and the earlier help, I did look at those but time was running out, needed to complete it last weekend and the Maplin fuse holder looked rugged enough to live in the boot. You never know in a fit of boredom I might change it over....lol

 

[Druk]

Most impressed with the installation.

DB...can you say if an estate has this 'rear prefuse board' and where it is located? Are the 'circuit 30' fuse holders a standard Merc item and do they simply plug in to this board?

Ta.

 

[jetset]

It won't work for the estate

Read with interest your towbar wiring, I'm trying to do same but I have LED rear lights and nothing I do will work. I even bought a smart relay where it stated that it would recognise lower voltage for lights and brakes, but didn't work. When I spoke to a fitter he sighed and said that he had to run wires to the front of the car and pick up from brake light switch and headlight switch.
I have tried this also but cannot find a 12v output from the switch, particularly as it has auto lights. I can't even find a headlight fuse, which may have helped.
Can anyone help?
Oh, my car is 2004 E320 estate (W211).
Andrew

 

[RSS]

What voltage is present for the side lights? I know when I was measuring mine (standard bulb version) I was expecting 12v but it was a lot lower as it runs the same lamp for side and brake lights just different voltages. My relay worked OK as the pick up wire is just to sense the signal so must have been above the threshold to activate it.

I can measure mine for you if you want so you can compare.

 

[ALAN PENNINGTON]

W211 e320 saloon jan 2008 tow bar & electrics

Hello everyone, I am new to this forum, in fact new to forums fullstop.
I have purchased a second hand swing away OEM MERC tow bar for my W211 saloon complete with the handle that fits in the boot to activate the tow ball swinging away under the car, however, most if not all the electrics out of the boot of the old car had gone by the time I got hold of the OEM MERC tow bar, I still think I have got a bargain but can anyone tell me if I buy a dedicated 13 pin electrics kit will I be able to fit this with the tow bar I have bought. The 13pin socket is still intact as part of the swing away ball, could it just be a case of wiring everything up to this socket or completely do away with it all together?