W124 Engine bay wiring looms

[grober]

This is a great article which goes into great detail on the type of wire suitable. Its for rewiring a V12!! so suitable lengths are not really available but might give folks a few ideas? V12 Uber Alles, Rewiring Electronic Throttle Actuators in a W140 Mercedes Benz

some of these suppliers are still current e.g. Custom Cable Design | Wire Harness Assemblies | Commercial Cable ----they may have British agents?

2mm cross section cable seems to currently run at about £1 per metre.g.
Buy Harsh Environment Wire Red LSZH equipment wire,2.00sq.mm 100m TE Connectivity 100G0111-2.00-2(S50) online from RS for next day delivery.

Thing to watch is that 240v rated cable may have slightly thicker insulation and therefore greater overall cross section than a 12v rated cable of the same current carrying capacity

 

[neilrr]

There's a bloke named josh on BenzWorld who rebuilds W124 & other MB looms - Mercedes Benz Defective Wiring Harness Rebuild - PICS! - Benzworld.org - Mercedes-Benz Discussion Forum .

He was asking USD$450 for an M104 loom about three years ago.

DYOR, Caveat Emptor, etc, etc.

 

[grober]

There's a bloke named josh on BenzWorld who rebuilds W124 & other MB looms - Mercedes Benz Defective Wiring Harness Rebuild - PICS! - Benzworld.org - Mercedes-Benz Discussion Forum .

He was asking USD$450 for an M104 loom about three years ago.

DYOR, Caveat Emptor, etc, etc.

He doesn't give much away on the spec ,lengths ,gauge of the wiring he used though does he?

 

[neilrr]

Find threads started by him for more info about him, his business & what he does. Seems to be good quality work & I don't see any complaints.

He says he's a qualified auto electrician & been doing this for about 20 years. Without knocking him or other electrical bods it's not rocket science, it's time consuming, fiddly work for someone who speaks 'wire' & 'electricity'. He's replacing wires using your old loom as a map, no moving parts involved.

IIRC the price can vary depending on whether new plugs, connectors etc are needed & possibly some other factors.

 

[grober]

Find threads started by him for more info about him, his business & what he does. Seems to be good quality work & I don't see any complaints.

He says he's a qualified auto electrician & been doing this for about 20 years. Without knocking him or other electrical bods it's not rocket science, it's time consuming, fiddly work for someone who speaks 'wire' & 'electricity'. He's replacing wires using your old loom as a map, no moving parts involved.

IIRC the price can vary depending on whether new plugs, connectors etc are needed & possibly some other factors.

I'm sure he does a good job and what he produces is OK. What I sensed was a post that promoted the service he was offering rather than helping people with detailed information of how to do it-which in itself is fair enough . The irony is that even if he told them exactly what materials he used there still would not be many with the inclination or skill to use it - so he hadn't much to lose anyway. It was a comment on the post rather than a criticism of the guy really - but that's maybe not how it sounded ?

 

[Apial]

so my single cam 103 engine is unaffected? What about the 3 litre 24v 104 engine is that ok too?

I've not heard of any M104 300/24 engines being affected.....yet.

 

[grober]

so my single cam 103 engine is unaffected? What about the 3 litre 24v 104 engine is that ok too?

Have a look at this thread [ you may want to sit down first.] you will see that the 300-24v ENGINE still hasn't moved to the "coils inside the camcover " design [ no distributor] that is a recipe for wiring being cooked! http://www.mbclub.co.uk/forums/mbclub-projects/29814-new-project-converting-my-300ce-300ce-24-a.html the old distributor design with HT plug leads - "in the wind" - may have been a trifle untidy but they didn't suffer engine heat degradation.

 

[Paul64]

Going for it.....

I set to last night - removed the old harness without too many problems and the only tool missing was a set of gynologically trained fingers for the A/C connection....

Can someone enlighten me as to what the 4-connection sensor is just forward of the glowplug water temp sensor? The wiring harness is in such poor condition, I can't really trace it without ripping it all to bits....

Many thanks


Paul

 

[Paul64]

See photo

 

[mejermy]

Do you have the EPC? Just had a look on mine, but not sure of your WDB first 6 numbers. The pix for the 124.131 and .191, which may be your's, don't show anything obvious other than possibly A0085423217, electronic idling control. I believe these later W124 diesels did have some electrickery. Where in France are you? I'm in Uzes and use a '93 S124 E250D down here.

 

[Paul64]

I am in Cagnes, close to Nice airport - 300D-24v. Great cars!
I checked out that number on Google and it comes up with the correct part - I'll check it out electrically and see if it needs replacement before putting everything back together again.
Thanks for the info - this, and the 500E site in the USA, have to be the most useful, interesting forums I've ever been on. Great to be part of it!

Paul

 

[grober]

I set to last night - removed the old harness without too many problems and the only tool missing was a set of gynologically trained fingers for the A/C connection....

Can someone enlighten me as to what the 4-connection sensor is just forward of the glowplug water temp sensor? The wiring harness is in such poor condition, I can't really trace it without ripping it all to bits....

Many thanks


Paul

Think its a thermal switch for some temperature dependent electrical device such as a cooling fan for the engine or aircon-- that's my guess from the picture/location

 

[Paul64]

OK, I found it on a website - it's the temperature sensor for the injection system and all figures for the resistances are available on line.
I will test it at lunchtime so I can order one today if required.

Thanks

Paul

 

[Paul64]

Came to put the new harness on this evening - all went well however, I have a 'spare' connector on the harness with a 2-pin plug.
The wires are purple/white and blue/red - I don't seem to have anywhere to put it!
Does anyone know what it's for? Perhaps its just a connection for an option I don't have though the car is automatic with 'Cats' and a/c so I think that covers most of the options....

Any ideas??

Many thanks,

Paul

 

[liam-neeson]

The 124 series was never fitted with the V6 engines The 280 you are considering is the M104 24v straight six which is a great engine, only sometimes prone to occasional head gasket failure - although Ive had a few and never had a problem. Ive never encountered the (bio-degradable) engine bay wiring loom problem either, athough as mentioned keep away from any car with running issues (miss-firing). The engine bay wiring problem isnt as common as some would have you think. I currently have a W124 saloon with the 3.2 verion of the M104 engine and it flies!!
Make sure the box changes smoothly without slurring or snatching.
They don't rust bad, check the wheel arches mainly, pop off the jacking point covers and check what you can there and at the bottom of the rear side windows, but thats usually only bad on earlier cars. If it twitches its bum as you pull away its the rear suspension control arm bushes (not a massive job). Listen for any creaks or knocks from the front suspension, balljonts can collapse, rare though.
All in all they are great cars, well built and not costly to run at all (as long as the above problems are avoided) and have a pretty timeless appeal. Ive had 8 W124s and never regretted buying any of them.

 

[Paul64]

What a difference! I tested the car last night after the replacement of the top harness and it started a lot more smoothly with a more realistic pre-heat time and afterwards, there was none of the 'hard' diesel sound of previous that used to take 5-10 seconds to fade away. I guess now the sensors are able to send reliable readings to the relay, bringing it back to original.
The temperature gauge also now reads correctly and the whole car seems happy again.

The new harness has a completely different sheathing over the cables - perhaps this is a non-self destructing new design to last till the car gets handed down to the kids....!

Paul

 

[balge]

Hi
have a '93 300TD, and the wiring on it looks fine...there is one tiny section of wiring with damaged insulation - but it looks like little teeth marks to me!

Just wondering if the under-bonnet temperature might have an effect on the plastic eg the hotter it gets the more likely it is to fail? Cars in warm places or with relatively hot running engines would be worse affected, a turbo engine must generate lots more heat than a NA, petrol engine more than Diesel, maybe a six more than a four..?


cheers

 

[grober]

Its deffo heat related---- problems supposedly first emerged in the Southern states of USA on the large engined models straight 6 and V8 petrols = high ambient and under bonnet temperatures

 

[balge]

Ah... not just me 'whistling in the wind' then...

Makes sense though...write it off to global warming then

cheers

 

[Paul64]

Not sure it's all heat related - I had a Daimler Double Six for a while and that ran so hot under the bonnet in the summer, there was a heat-haze coming off it in traffic!
That had no problems with wiring, even after 15 years and as far as I know, it's still going strong back in England. Though possibly not as reliably as a Merc....

Most of the electrical side of those was by "Lucas, Prince of Darkness" which doesn't have the best reputation for quality.
I'm sure the product used for the insulation on our mid-90's Mercs was to blame as there's such a spread of problems round the world, even in cold places, it's not just a few bad looms. Certainly, heat wouldn't help but if it's the wrong stuff, it's the wrong stuff!

Paul