W124 wiring advice

[shanksy]

yep, the harness definitely has the fuse block attached, just can't see the fuse box to attach it

 

[mejermy]

12v feed

The attached are of X4/1 which is what you're looking for. It is high up above the pedals. The pix are indeed poor on the WIS, from which the ones I sent you came. My pix are from my LHD, so your X4/1 is prob RHS of the RHD column.

I think the WIS instruction explain that the unfused 12v feed harness connects from X4/1, goes out into the engine bay to the auxiliary, small fuse box (in your pic or the components you have) and then back to join with the male single pole 12v feed to the interior heated seat harness.

Hope this is clear

 

[mejermy]

Meant to say back inside the cabin again. MB never make it easy ehh?

 

[BillyW124]

You mean you cant see the fuse box from the knee panel upwards?

Its pretty cramped up there on that right corner!

To make it easier, you'll have to undo the screws in the fuse box to reveal the very back part where all the relays are, you then can just make out a gap amongst the hundreds of wires to feed the fuse through. Since you have removed the knee panel from the fuse box downwards outside of the car you should be able to see your footwell.

 

[mejermy]

You can see the fuse box, and it's (IMO) the best way out and back in. although you will see the WIS says to use a grommet bay the heater box. X4/1 doesn't have a cover. If you unscrew and partly lift out the fuse holder tray (one screw front centre) it's a lot easier to thread something through.

 

[shanksy]

Cheers guys i'm with you now, that should be pretty straight forward to finish off then.
I've put all the trim back so I can use the car in the week so i'll have to finish it off next weekend.
So wish I had a garage or even a drive to work on, hate working on a main road thinking someones gonna have me door off every 5 mins.

 

[brigadier]

A spacious, heated garage would sure be nice. I have drive to work on but still - it's too cold to feel motivated.

 

[shanksy]

Today I managed to hook up the remaining section of the harness (man that was fiddly trying to feed through to the cabin!).

Not having much luck with getting the pads to warm up though.
My first attempt was just to connect up pins 1 & 2 to the first pad, pins 3 & 4 to the second. No joy there so just tried reversing the polarity of the pad wires as wasn't sure if red/green or black was supposed to be positive, again no joy.

I'm wondering what next to try, unfortunately I don't have a multimeter at the moment so cant check the feeds. The new switchgear does light up correctly on both settings though.

Anyone with ideas ?

 

[brigadier]

My first attempt was just to connect up pins 1 & 2 to the first pad, pins 3 & 4 to the second.

I'm sure that's how original mats are set up on my heated seats. Polarity shouldn't matter for pads. You should really get a multimeter and get a readout from all the pins on both settings. If you work on your car yourself you should ideally get automotive dmm with duty cycle measurement which can be used to set mixture etc.

 

[mejermy]

Wiring

Lee - have just fired off a direct email with a wiring diagram attached due to the very large file size. Came across this in the last day or two and it agrees completely with my harness. You'll see the double connection of the KBu left and KVi right plug pin 3 from both pin 2 of each plug and pin 8 and 2 respectively of the relay. Surely if you copy these connections to the new pads they'll light up? (In a good way!!)

M

 

[shanksy]

Thanks Malcolm, i'm reading that diagram as wiring the 2 x positive connections on the left pads to pins 2 and 3, and the 2 neg connections to pins 1 and 4.

@Brigadier - Yes, definitely something I need to be investing in, i've an outdoor temp gauge harness to install as well at some point

 

[shanksy]

Just attempting another rewire now, do you guys know if the grounded pins have to be the open topped ones rather than solid topped as in the pic ?
Cheers

 

[brigadier]

Are they from the pads? I think the left one is full with solder as it should be.

 

[shanksy]

No, these were from other bits I had lying around. I thought i'd use them and make up a couple of male connectors for the seat connector blocks to plug into.

Seemed to be that the open ended ones had copper wiring, the solid ones were all silver? wires. Wasnt sure if it was by design or as you say just not fully soldered.....

 

[shanksy]

right here goes round 3.............

 

[shanksy]

ok so Pos feeds to pins 2 and 3, neg to 1 and 4 failed also

 

[shanksy]

I'm gonna have to get the multimeter tomorrow and check im getting voltage at the seat plug end first.
Time to chill with MOTD for a bit now.......

 

[shanksy]

ok, i'm not getting much at the pins im afraid, with heat setting 2, I get a quick register of 0.06 on pins 2 and 3 before dropping down to zero, nothing on pins 1 and 4.

I am testing with the ignition on but not the engine, using a screwhole in the chassis as ground. Does this sound like I am not getting the required power to the connector or am just using the multimeter wrong ?

 

[shanksy]

Just tried the red SRS pin from the missing passenger seat and got 1.7V so the multimeter is working fine, must be the seat connector has no power.
The switches light up fine and you can hear the relay clicking when switching on/off or between settings 1 and 2.
Not sure where to check next............

 

[brigadier]

Since the relay seems to be working I would check if you have +12v from the feed - the one with own fuse.