W124 wiring advice

[shanksy]

Hi all,
I will be finally undertaking the install of my heated seat wiring harness this weekend.
Being a bit wet behind the ears when it comes to electrics i've done as much research as I can but just wanted a bit of advice on where a couple of pieces of the harness go.........

I need to know :

a) Where the backlighting connector is expected to connect to
b) The best route for the 12v feed to go through the firewall.
c) Once the loom is in, can I join the wires from the new carbon pads up at the point where the seat connectors are ? The wires into one of the seat connectors has 5 wires; 3 x Blue/Black, Brown/Yellow and Brown. Which of these wires would I use ?

I've attached some pics of the harness and the connectors/wires.

Appreciate any help
Cheers

 

[shanksy]

The 2nd pic is the backlight connector, the third is the connection to the seat.

 

[shanksy]

Standard connection for each Carbon pad.......

Full wiring diagram for the harness.......

 

[brigadier]

The 5 pin long connector goes behind right hand side plastic cover in drivers side footwell under steering wheel. There is like a common bus with few of those 5 pin connectors. I had wiring harness from w126 and it didn't have that single 12v connector - only the 5 pin and it's working fine.

edit. I'm guessing 12v feed might just connect straight in one of the fuse terminals. iirc there is female round plugs under the fuses - you have to pull the fuse panel up and see from underneath. Disconnect battery negative of course while doing all this. So you don't need to go through the firewall. just take panel below steering wheel out and you have access to fusebox underside.

Regarding the new pads the brown should be negative supply and blue/black positive. But you can check when you connect it up. There will be 2 pads in each seat, so you can use one pair of black blue for one pad and another for second pad.

The ground connects near the the switches

 

[shanksy]

Can't thank you enough for that info mate, well helpful.

Just to clarify on one thing though, so both the brown and the brown/yellow will be the 2 x negative supply ? With only 3 x blue/black positive, will it matter that one pad has 2 x positives wired to it and the other pad has only 1 ?

Thanks again for your first post, i'm feeling a lot more confident about spending the day freezing my nuts off doing this!

Did you sell your Waeco's to Azaman in the end ?

 

[brigadier]

Yes. The top 2 pins on your picture should be for one mat and bottom two for the other one. Still have the waeco's. I'm too lazy to put them in ebay or classifieds - as well as other bits.

edit: by the way are you using the same connectors or something else? If you don't use them maybe i can have just the plastic part. Harness I had was from w126 and the connectors didn't fit.

 

[shanksy]

I don't have anything I can use to plug in the wired carbon pads to the existing connectors, more than likely i'll cut the connectors off and just connect the wires up using a 15A terminal block or something.
If thats how it ends up going, i'd be happy to post you the connectors when i'm done.

 

[mejermy]

Just completed this on my E250D today!! I have the original harness, as yours, but chose to keep the dk-schweizer switches and harness. Do you have the relay? I can see you have the plug to it. Do you have smaller the main feed harness which takes power from the unfused connection beside the steering column back into the engine compartment to the auxiliary fuse fitting, and back agian into the footwell to join with the single pole male? I have tried to upload the WIS instructions, but too big a file. If you post/pm your address I'll email directly. I will be using the MB harnesses I have in another W124 myself, joining to Systafex mats from Germany. I believe that the MB 4 pole mat connect supplies power on setting 1 to both mats in series from pin 1, and in parralel from pins 2 and 3, with pin 4 ground. This tells you what to join where therefore. This is from memory-suggest you do a DMM check.

 

[shanksy]

Cheers mejermy, PM sent...

 

[mejermy]

Ahead of you Lee. I remembered eventually that we communicated a week or two ago, so I had your address and have PMd the file.

Malcolm

 

[brigadier]

That's quite complicated! I'm pretty sure that pin1 and pin2 is mat #1 and pin3 and pin4 is mat #2. So if on first setting pin1 is 12v and pin4 is ground then relay box joins pin2 and pin3 to make mats connected in series? and then on setting 2 pin1 and pin3 is 12v and pin2 and pin4 is ground - hence parallel?

 

[mejermy]

That's what I reckon. I think I picked that up from a US site, but it's easy to check with a spare battery and jury rigged wiring on the garage floor. I didn't bother due to deciding to go with the after market kit completely. Shanksy doesn't seem to have the relay or the feed harness though if all his kit is in the pix. Also a fuse holder and small bracket for it is required in the engine compartment.

 

[shanksy]

Just reading through the WIS doc at the mo...........

 

[brigadier]

How come w126 harness I got wired in my w124 doesn't have the separate feed - just the 5 pin connector for power and everything's working?

 

[shanksy]

Cheers for the doc malcolm, the previous harness pics were just ones i'd found elsewhere online, i've uploaded a pic of everything I have.
Still reading ..............

 

[mejermy]

I found this very illuminating

300e - Adding heated seats - Benzworld.org - Mercedes-Benz Discussion Forum

Regarding brigadier's W126 harness; dunno. But the GyBu wire that goes to pin 4 and the KY wire that goes to pin 5 on the footwell 'special equipment' connector X30 seem to provide power and light to the switches. They then switch the relay to bring in high current for the pads through the connection at X4/1, by the side of the column, which is always hot. This is the wire which should connect from X4/1 to the 16A fuse in the small auxiliary fuse box in the engine compartment and back into the cabin to join with the male single pole.

 

[brigadier]

Looks like it's all there after all

 

[mejermy]

Would agree all there. The bracket for the auxiliary fuse box is A1245455840 IIRC and there's a clip which fits in that to hold the auxiliary box.

Bon courage Lee

 

[shanksy]

I'm a little bit confused now guys, when you talk about pins 1-4 are these just the pins in the seat connector from left to right following a Z shape ?

 

[brigadier]

Regarding brigadier's W126 harness; dunno. But the GyBu wire that goes to pin 4 and the KY wire that goes to pin 5 on the footwell 'special equipment' connector X30 seem to provide power and light to the switches..

The w126 harness has 3 pins in 5 pin connector