Mercedes-Benz Forum banner

1 - 15 of 15 Posts

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #1
Hello comorades. So I am confused on where the wiring harness are that get fried on the M120 V12. On the picture I posted, I circled the parts that I thought were the wiring harness that get fried, but from some recent reading, I'm thinkin I was wrong.

Could some one please clarify it for me?? It would help a lot to post a pic and or a video.
Sent from my DROID2 GLOBAL using AutoGuide.Com Free App
 

Attachments

·
Premium Member
1999 S600 Sedan, 1999 S600 w/ 4-pl seating, 1995 S600 Coupe, 2-1992 600SEL's, 2002 ML55, 1998 SL600
Joined
·
2,425 Posts
Happy to help:

The two harnesses that are the subject of much frustration are:

The engine harness: Connects the spark plugs, runs under the central plastic molding you have circled in red. This harness is the 'minor' harness as it is relatively simple to replace as it is all located in the engine compartment.

The body harness: Connects the computer cabinet (passenger side of engine compartment) to every other system in the car. This harness is the 'major' harness as it runs all over the engine compartment, through the firewall and even into the passenger side of the interior. This will take about 6-hours to REMOVE, about 7-hours to RECONNECT.

To make sure your harnesses are FAILING, make sure you see the insulation flaking off, bare wires exposed, or a heck of a lot of dust in the channels the wires reside in. Many of these harnesses were replaced by MB and the replacements are NOT made with the soybean coating that is flaking off in the 'biodegradeable' harnesses.
 

·
Premium Member
1997 S600 (sold)
Joined
·
4,660 Posts
Happy to help:

The two harnesses that are the subject of much frustration are:

The engine harness: Connects the spark plugs, runs under the central plastic molding you have circled in red. This harness is the 'minor' harness as it is relatively simple to replace as it is all located in the engine compartment.

The body harness: Connects the computer cabinet (passenger side of engine compartment) to every other system in the car. This harness is the 'major' harness as it runs all over the engine compartment, through the firewall and even into the passenger side of the interior. This will take about 6-hours to REMOVE, about 7-hours to RECONNECT.

To make sure your harnesses are FAILING, make sure you see the insulation flaking off, bare wires exposed, or a heck of a lot of dust in the channels the wires reside in. Many of these harnesses were replaced by MB and the replacements are NOT made with the soybean coating that is flaking off in the 'biodegradeable' harnesses.
A slight correction. The engine harness down the center of the engine connects the fuel injectors. The spark plugs on the earlier LH injection system are fed by the typical thick high voltage wires from the distributor caps.

Besides this "upper" engine harness, there is also what is often called the "lower" engine harness around here. This smaller harness contains wires between the alternator and starter, the oil pressure sender, and a couple other things. It also degrades. There was just a nice thread on this a couple of days ago.

We had a healthy debate on whether one needs to replace the entire "body" harness. Whether it is sufficient to replace only those wires that are exposed to heat cycles in the engine compartment. There is no doubt or debate that a correct and full repair is to pull and replace the entire harness, but as Stryker mentions, it is a signficant undertaking in both labor costs and harness cost... read a few thousand dollars. It may be sufficient to replace only the wires of the harness that are visibly degraded (pin to pin replacement, not splicing sections). But, one needs to decide for himself what kind of repair to do of this harness should it need it.

Brett
 

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #4
Thanks guys, you pretty much contribute so much you basically own the forum. this makes a lot more sense now. i know that the previous owner had the engine harness, or the upper harness done at an MB dealer, but where should i look to check and see if the body or lower harness is degrading? isn't it like some where near where i circled green? or under the diagnostic plug in? Im not having issues, i am just curious. (fingers crossed)
 

·
Premium Member
1997 S600 (sold)
Joined
·
4,660 Posts
Lower engine harness as I said contains wires to and from the back of the alternator and the starter and also the oil pressure sender located at the oil filter housing. See Merc S500's thread that I posted.

I have never seen an early car, so I'm not as familiar with the body harness, but it is basically the main harness that connects to the computer modules in computer box under the hood.

Brett
 

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #6
Lower engine harness as I said contains wires to and from the back of the alternator and the starter and also the oil pressure sender located at the oil filter housing. See Merc S500's thread that I posted.

I have never seen an early car, so I'm not as familiar with the body harness, but it is basically the main harness that connects to the computer modules in computer box under the hood.

Brett
im really curious to find out what my insulation looks like, i know that the first owner was the CEO of MB of Denver (Murray Imports), the second was the president (yes they're two separate people), and the third owner of which i bought the car claimed that the quote "entire wiring harness had been re-done". i know that the upper wiring harness was redone for sure, but im not to sure about the lower one. but i have no warning lights, and all of the lights work as well. the car never mis behaves, and the only time it has not started was because i accidentally flooded it. it has around 121k miles on it, and all three previous owners garaged it it's entire life. unfortunately i don't have a garage :( so the car has to sit out side. but during the winter where it stays around zero degrees, i think that the insulation would last longer because its not so exposed the the immense heat from the V12. but i knew that i was taking a risk when i decided all i could have was the V12, but it is totally worth it :D
 

·
Premium Member
1999 S600 Sedan, 1999 S600 w/ 4-pl seating, 1995 S600 Coupe, 2-1992 600SEL's, 2002 ML55, 1998 SL600
Joined
·
2,425 Posts
Bomb: I wouldn't worry about your wiring, given the previous owners, the likelihood is you already have had your wiring swapped out.

The problem became known within a couple of years of the wiring's introduction. ALL of MB cars in the early 1990's were outfitted with this 'biodegradeable' wiring harness to keep up with the latest things 'environmental'. Only with long-term testing were they able to determine these things don't hold up and cause major problems. Once the dealers caught wind of what was going on, they took it upon themselves to switch out what cars they could while under warranty. MB, wrong-headed as it was, never issued a general recall on the wiring harnesses.
 

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #8
yeah im not too worried, i think im pretty safe. i was just curious to see if there was an easy access point to check and see if the insulation was crap or not
 

·
Premium Member
'93 600SL , 2009 C350
Joined
·
184 Posts
Good Day , having rebuilt my wire harness I would pop the side cover off the passenger Throttle body (ETA is their term I think) ... mine were totally decayed. These wiring issues were tied to cheap crap that Bosch supplied ... I think most of the body harness was supplied by someone else or to a different spec. Only certain sections had the decay issue. For example my passenger MAF wire needed to be rebuilt while drivers side was solid ... totally different wire. I don't buy the biodegradable psycho babble BS that the Germans dreamed up to cover their butt. That said best of luck , hope your problems are already taken care of. The ETA's are about $750 a piece to be rebuilt ... or if you are good with a soldering iron... $20 LOL ... cheers
 

·
Premium Member
Joined
·
867 Posts
I don't buy the biodegradable psycho babble BS that the Germans dreamed up to cover their butt.
They didn't make anything up. During the 80's the soybean was emerging as a hot product that would save the third world and the environment. The soy oil could be used to make a plastic that would replace dino oil based materials.

The soybean is also full of protein so it was thought it would solve world hunger as well as provide a cash crop to build up third world countries.

Alas, it was a bit too good to be true. A telco engineer neighbour of mine was telling me how they put miles of this cable into the phone networks only to have to pull it all out again a few years later. Many companies got burned.

The oil still has applications, such as making a foam for house insulation, but is not the miracle it was intended to be.

The degradation rate of the harnesses in cars depends on the amount of heat and moisture it gets exposed to. The 'totally different wire' you saw could well have been a harness already replaced.

P.S. Classy looking SL you've got there.
 

·
Registered
2003 S55 AMG Kompressor
Joined
·
361 Posts
And it also is not "cheap crap that Bosch supplied", the wiring was supplied by Delphi
 

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #12
Even though the soybean wiring is a crap idea now, at the time it was an awesome idea! I don't know where you live, but where i live there are thousands upon thousands of dead cars in my town, and if they all had environmentally friendly wiring, we wouldn't have nearly the same issues with these dead cars that some of us call lawn ornaments that we have now. :thumbsup: a lot of bits and pieces in an S-class are actually recycled. the W221 even won more environmentally friendly awards than the prius!

Plus any S-Class is quote on quote from Jeremy Clarkson "a showcase of everything that can be done, and what everyone else will be doing very soon". so with being on the very razor sharp edge of current technology, you can never see what's ahead and how it's all going to pan out.
 

·
Premium Member
Joined
·
867 Posts
"...and what everyone else will be doing very soon".
In some cases though, it is more of a cautionary tale. Had the wiring lasted at least 10 years before giving trouble it might not have been so bad. As far as the industry is concerned, 10 years is what is meant by "life" (as in "sealed for life" transmissions). In Europe, it is expected that cars will be recycled at this time so if they blow up, no big deal.

Here in Australia and the USA we tent to hang on to our vehicles much longer so these things bother us much more.

The fact that wiring issues showed up so soon during the models production run is an embarrassment. It's another pointer to the strain MB were under to get the W140 out the door.
 

·
Registered
140 600 1991
Joined
·
221 Posts
I saw recently a program on ultra-modern huge mining devices and they say that high part of steel today used to build them comes from 100+ yrs ago. This steel is just receycled already a few times as these huge machines die eg every 40 years. Kind of piece of history inside them... :)
 

·
Registered
1992 600SEL and 1990 ford taurus GL
Joined
·
270 Posts
Discussion Starter #15
In some cases though, it is more of a cautionary tale. Had the wiring lasted at least 10 years before giving trouble it might not have been so bad. As far as the industry is concerned, 10 years is what is meant by "life" (as in "sealed for life" transmissions). In Europe, it is expected that cars will be recycled at this time so if they blow up, no big deal.

Here in Australia and the USA we tent to hang on to our vehicles much longer so these things bother us much more.

The fact that wiring issues showed up so soon during the models production run is an embarrassment. It's another pointer to the strain MB were under to get the W140 out the door.
Wow I can't imagine only having a vehicle only last ten years. Over here, or at least in my location, the average car is probably around 15 years old. With well over a hundred thousand on it. A ten year old car here is basicly still new to us. We actually just had a survey that said we own our cars on average of ten years.

I believe mb was under differnt owners when they were trying to get the 140s out the door. They needed them out for the 220s. And like u said the wiring harness, plus the 140 was "too expensive" for them.

Sent from my DROID2 GLOBAL using AutoGuide.Com Free App
 
1 - 15 of 15 Posts
Top