Engine (Upper) Wiring Harness

[fastcar]

Vehicle: 1992 500E.

I have been hearing and reading a lot if comments about the wiring harness:
What does one look for on the harness for signs that is needs to be replaced, My motto is if it working well ,, why fix it..
I know the Harness is not cheap,, so if it's still in working order why change it,,, comments please.
Does anyone out there have photos of the harness ,, if so,,, please send,

 

[gsxr]

Re: |Wiring Harness

You're looking for the insulation cracking and coming off the copper wire. Here are a couple of sample photos. Even if the harness looks ok at the ends of the wire, it's a good idea to slice open a couple inches of the protective sheath, and look inside. You can tell right away if the harness is bad or not.

 

[Glen]

Re: |Wiring Harness

I can almost guarantee with 100% certainty that if the ends look like the pictures Dave posted, you will be horrified to see what's under the sheath further up. Many, if not most cars run "fine" with a bad harness until the another job requires you to move the harness, then suddenly the car starts misbehaving, running poorly, sometimes throwing codes, and in unfortunate cases, frying the computer.

 

[gerryvz]

Re: |Wiring Harness

Here are a few other photos of my own harness from some years back. There was nothing wrong with the harness, but I decided to replace it (proactively). After removing it, I split open the outer sheath and the attached photos show the results. The car had about 80,000 miles on it at the time.

Cheers,
Gerry

 

[BlackDogBD]

Re: |Wiring Harness

Those pictures scare me....like the trees in the Wizard of Oz.

 

[500ESpain]

Re: |Wiring Harness

I can almost guarantee with 100% certainty that if the ends look like the pictures Dave posted, you will be horrified to see what's under the sheath further up. Many, if not most cars run "fine" with a bad harness until the another job requires you to move the harness, then suddenly the car starts misbehaving, running poorly, sometimes throwing codes, and in unfortunate cases, frying the computer.

That's exactly what happened to me. The car was running all right until I moved the harness while doing other jobs. I've ordered a new one and I'll be installing it soon. Let's see what I find inside the old one.

Happy new year!

 

[gerryvz]

Re: |Wiring Harness

Definitely take a lot of photos and post them here!

Cheers,
Gerry

 

[Swe500E]

Re: |Wiring Harness

Do any one now the MB spare part number for this harness? :?:

I?m at work so I don?t have access to EPC

 

[gerryvz]

Re: |Wiring Harness

It depends on the VIN / model year of your car, but there is a thread detailing this at 500ecstasy.com here:

http://www.500ecstasy.com/forums/showthread.php?t=4761

For the record:

For early cars: (up to VIN 840526) - 124 543 95 26.

For later cars: (from VIN 840527) - 124 440 20 06.

Cheers,
Gerry

 

[500ESpain]

Re: |Wiring Harness

124 543 95 26

343,65? (493$) +19%VAT + Shipping from www.speed-autoteile.com.

 

[Swe500E]

Re: |Wiring Harness

Thank you guys!

Edit; Is there any more harnesses on the M119 that gives up?

This was some year ago, maybe my memory is bad but if i remember right;
Im member in a swedish MB board www.mbsca.com/forum and another member there hade some problems with his C140 600.
One harness on the M120 V12 is locatead right under the headers (Hot!) and this one including the wire to the oil pressure, so when the harness became to bad the car lost signal from the oilpressure and shut down the engine to protect it.

 

[500ESpain]

Re: |Wiring Harness

You're faster, Gerry

 

[gerryvz]

Re: |Wiring Harness

:tacho:

 

[gsxr]

Re: |Wiring Harness

Edit; Is there any more harnesses on the M119 that gives up?

Yes. The harness which goes to the starter and alternator also fails due to heat damage, and includes the wires which go to the oil pressure & oil level senders.

This was some year ago, maybe my memory is bad but if i remember right; Im member in a Swedish MB board. Another member there hade some problems with his C140 600. One harness on the M120 V12 is locatead right under the headers (Hot!) and this one including the wire to the oil pressure, so when the harness became to bad the car lost signal from the oilpressure and shut down the engine to protect it.

That's the one! I already replaced it on my E500 and I have a new one ready to install on my 500E. Here are a couple of photos:

 

[gerryvz]

Re: |Wiring Harness

Dave, what's the price on that lower harness? Are there early and late series part numbers?

I recently replaced that same harness on my 560SEC as the wire had corroded at the attachment to the alternator (old age; it was 20 yrs old). This SEC harness at one end attaches to the battery and at the other end to the starter and alternator, with a few branches off. Took about an hour to replace, but there is much more room underhood on the SEC to work than the E500E has. I think the cost of the SEC harness was around $125-150 IIRC.

Cheers,
Gerry

 

[gsxr]

Re: |Wiring Harness

It's the same part number for all years of the 500E, p/n 124-540-27-30. Current MSRP in the USA is $284 - ouch. That's a lot more than it was a few years ago.

 

[askd9280]

Re: |Wiring Harness

Recently all my coolant over flowed onto the overflow hose. The shop checked for any pressure leaks in the cooling system but found none. Apparently they said it was my aux fans not properly functioning. One fan has a busted motor. Had new auxiliary fans replaced. However, according to the shop the fans were not working properly due to some sensor portion of the upper engine wiring harness p/n 124 543 95 26?

Isn't the aux fan control part of the body mounted engine harness 124 543 41 32?

Appreciate all the advise I can get.

Thanks.

 

[Christian_K]

Re: |Wiring Harness

One Plug of the upper wiring harness connects to a coolant sensor which is only there to switch the aux fans at 105-107° Celcius. So this is correct.
However still, the car normally shouldn't go that high with temps (except full AC on, stop and go traffic inside a city with very very high outside temps) and even if, the over-pressure valve inside the cap of the coolant reservoir will let all overpressure go away.

 

[askd9280]

Re: |Wiring Harness

Got it. Double checked and the wires insulation in the coolant sensor are already gone. Guess this caused the aux fans to not function properly.

The cap release valve probably wasnt enough the coolant oozed out on the bottom right side wheel well guess this is where the reservoir overflow hose connects to.

Thanks. for the help just wanted to make sure I was changing the correct harness.

BTW, has anyone heard of problems with the engine wiring harness body mounted p/n 124 543 41 32. This is a very expensive part? It the most expensive among the three harnesses.

Thanks.

 

[gsxr]

Re: |Wiring Harness

BTW, has anyone heard of problems with the engine wiring harness body mounted p/n 124 543 41 32. This is a very expensive part? It the most expensive among the three harnesses.

The body mounted harness has very little to do with the engine, and it is an extremely rare failure. So rare, that harness has never been ordered in the USA, as the part number does not appear on the MBNA price list (neither does the 93 or 94 harness - the number you list is for 92 only). If someone had ever bought one, it would be on the price list. It's about $3k USD (approx, based on Euro pricing) and an absolute nightmare to replace as a huge amount of disassembly / reassembly is required. The 93 & 94 body harnesses are even more expensive: ~$4k USD! Yikes. Good thing they last a long time...

 

[askd9280]

Re: |Wiring Harness

ok got that.

Thanks a lot.

 

[askd9280]

Re: |Wiring Harness

Been going through the wiring harness posts but could not find a discussion on the difference between the two different part numbers for the upper engine harness.

Would anyone know the possible differences in the two: p/n 124-543-95-26 and p/n 124-440-20-06

Thanks.

 

[Christian_K]

Re: |Wiring Harness

Been going through the wiring harness posts but could not find a discussion on the difference between the two different part numbers for the upper engine harness.

Would anyone know the possible differences in the two: p/n 124-543-95-26 and p/n 124-440-20-06

Thanks.

My cable guy from Stuttgart told me once as i was asking the same, the only difference is that in one of the two there is a additional "heat-resisting hose" inside the cable-insulation that goes to the MAF. Which one, i don't remember. It's out of concern anway he told me.

 

[gerryvz]

Re: |Wiring Harness

So rare, that harness has never been ordered in the USA, as the part number does not appear on the MBNA price list (neither does the 93 or 94 harness - the number you list is for 92 only). If someone had ever bought one, it would be on the price list.

Is this true ?!? I've never heard that a SKU is listed on the MBNA price list ONLY if it's ever been ordered in the US. IMHO sort of defeats the purpose of a price list, eh? Can you let me know where you heard this from and/or experienced this?

Cheers,
Gerry

 

[Silver Arrow]

Re: |Wiring Harness

How long does this wiring harness install take, average first-time DIY?

 

[gsxr]

Re: |Wiring Harness

Is this true ?!? I've never heard that a SKU is listed on the MBNA price list ONLY if it's ever been ordered in the US. IMHO sort of defeats the purpose of a price list, eh? Can you let me know where you heard this from and/or experienced this?

I have purchased several items over the past 5+ years that were not on the USA price list. I would estimate the cost based on Euro pricing. I call the dealer and verify the part number is in stock in Germany, and orderable (not Comm Blocked). When the order is placed, MBNA has to add it to the US price list. Afterwards (within a few weeks or months) the price will appear at places like parts.com where previously no price showed at all. I've personally experienced this multiple times, probably at least a half-dozen. It almost always applies to parts which are Euro-only, but I have found some US-spec parts which fall into the same scenario, such as the body wiring harness.

Check it out for yourself: 124-543-41-32 is not on the US price list (call your dealer to prove it), but you can look it up on Euro price lists:

http://mbspecialist.com/mercedes_webcatalog/item/1245434132/
http://www.mercmania.pl/cennik.php?kat=A&numer=1245434132

Note: The second URL is showing prices from several years ago - first URL has more current pricing.

 

[bing]

Re: |Wiring Harness

Double checked and the wires insulation in the coolant sensor are already gone. Guess this caused the aux fans to not function properly.

this seems to be one of the tell tale signs when top harness is toast. Had the same problem sometime back when aux fans kept cutting in - ended up replacing 2 sensors , refrigerant and temp. But it turns out it was the wiring on the temp sensor that sits on intake manifold. Drove me mad, and in the end it was time to change the harness anyway.

 

[gsxr]

Re: |Wiring Harness

Been going through the wiring harness posts but could not find a discussion on the difference between the two different part numbers for the upper engine harness.

Would anyone know the possible differences in the two: p/n 124-543-95-26 and p/n 124-440-20-06

I've had them side by side and the only difference I could find is the color coding of the insulation was different for some wires. All the connectors were identical and I think you could interchange them if needed. However, I have not yet actually tried using an early harness on a late car, or vice-versa.

I've never heard of the additional internal heat insulation, but I've also never cut both apart to find out...

 

[Christian_K]

Re: |Wiring Harness

I just checked my old emails again with the cableguy and he said that one of the two has a so called "Glasseidenschlauch", translated "Fibreglass Hose" at the HFM (MAF-connector cable) cable under the insulation.

 

[askd9280]

Re: |Wiring Harness

My cable guy from Stuttgart told me once as i was asking the same, the only difference is that in one of the two there is a additional "heat-resisting hose" inside the cable-insulation that goes to the MAF. Which one, i don't remember. It's out of concern anway he told me.

Ok. I thought that there might be diffrences in the following:

1. Pin assignments in the wiring

or

2. Pin connectors having different sizes

or

3. Plugs might be different

That heat resisting hose seems to be a good feature that warrants ordering the later part number.

Thanks.

 

[askd9280]

Re: |Wiring Harness

I've had them side by side and the only difference I could find is the color coding of the insulation was different for some wires. All the connectors were identical and I think you could interchange them if needed. I've never heard of the additional internal heat insulation, but I've also never cut both apart to find out...

Would the different color coding of the insulation lead to a diffrerence in the pin assignments in the head end (i.e. the big plug that connects to the main computer? Just wondering?

 

[Christian_K]

Re: |Wiring Harness

Would the different color coding of the insulation lead to a difference in the pin assignments in the head end (i.e. the big plug that connects to the main computer? Just wondering?

No, pin assignments and connectors were always the same.

 

[gerryvz]

Re: |Wiring Harness

Interesting. I'm going to chat about this with some sources (including Tom Hanson at the Classic Center) and see about the mechanics of this.

Cheers,
Gerry

 

[Allgonquin]

Re: |Wiring Harness

"How long does this wiring harness install take, average first-time DIY? "


I would budget a day to do it. Actual work time is much shorter, but setup, pondering and fiddling time for me took a while. I took photos of everything before, and it took me a while to figure out a few things, like how to open the sort of clamshell connector where the main harness goes through the firewall. Overall this is not a difficult job, but of course you want to take your time and do things carefully.

Rgds,
Chris

 

[Silver Arrow]

Re: |Wiring Harness

"How long does this wiring harness install take, average first-time DIY? "


I would budget a day to do it. Actual work time is much shorter, but setup, pondering and fiddling time for me took a while. I took photos of everything before, and it took me a while to figure out a few things, like how to open the sort of clamshell connector where the main harness goes through the firewall. Overall this is not a difficult job, but of course you want to take your time and do things carefully.

Rgds,
Chris

Thank you, Chris!

 

[Silver Arrow]

Re: |Wiring Harness

-Fingers crossed-

Anyone know of a DIY for installing a new replacement engine wiring harness......?

I'm hoping to do this install very soon, it would be a great help.

 

[gerryvz]

Re: |Wiring Harness

No DIY needed.

1) Remove everything on top of the motor so that the existing harness is easily accessible.

2) Take photos of connectors and routing if you need to

3) Lay the new harness out on top of/next to the old one, including all connectors

4) Remove connectors and replace them with same connector from new harness, one by one

5) Lift up old harness as you remove sections of it and put new harness into place (as good as you can)

6) Ensure new harness is in place and all connections routed like old one was

7) OPEN UP OLD HARNESS and take PHOTOS of connections, wires, and flaked off insulation

8) Post photos on this site

9) Crack a beer (or three)

Cheers,
Gerry

 

[Silver Arrow]

Re: |Wiring Harness

No DIY needed.

1) Remove everything on top of the motor so that the existing harness is easily accessible.

2) Take photos of connectors and routing if you need to

3) Lay the new harness out on top of/next to the old one, including all connectors

4) Remove connectors and replace them with same connector from new harness, one by one

5) Lift up old harness as you remove sections of it and put new harness into place (as good as you can)

6) Ensure new harness is in place and all connections routed like old one was

7) OPEN UP OLD HARNESS and take PHOTOS of connections, wires, and flaked off insulation

8) Post photos on this site

9) Crack a beer (or three)

Cheers,
Gerry

Haha - thanks Gerry - I guess my question is, more precisely, is there a specific order that is "better" to remove andd reconnect the various ends of the harness in...? Should I start here versus there, or go clockwise, or whatever....? Any particular tools required?

Any tips would be much appreciated!!

 

[gerryvz]

Re: |Wiring Harness

Generally speaking, I'd do it from the ends of the tree branches and work toward the trunk, but that's just me.

It's probable that you're going to break some plastic clips and such, which are heat-baked and age-brittled. Make a note of the connectors/clips that you break, and you will probably want to look them up and put an order in to replace them. Be VERY careful on these pieces and you may well save a few of them and be able to re-use them. But there are going to be some plastic bits that just crack/crumble as you remove them. Just wanted you to be prepared for that....

Cheers,
Gerry

 

[Silver Arrow]

Re: |Wiring Harness

Here are a few other photos of my own harness from some years back. There was nothing wrong with the harness, but I decided to replace it (proactively). After removing it, I split open the outer sheath and the attached photos show the results. The car had about 80,000 miles on it at the time.

Cheers,
Gerry

Well, today I installed a brand new replacement upper engine wiring harness on my '93 500E - proactively, because I felt that it was just time to do it.

A few details while they're fresh in my mind:

- Upon removal and inspection, the wiring harness on my car was the factory-original one with an 11 Mar 92 date of manufacture.

- Even though my 500E has relatively low miles (63k + change), the harness looked identical to the photos that Gerry posted of his harness - many many cracks in each and every wire's insulation, brittle plastic clips, etc. It's amazing that these cars even start and run with this kind of degradation. The moral here is: mileage means nothing. If it's the year 2011 or later and you have a 500E with the original harness, then it needs to be replaced immediately. My opinion is that damage can be done to various electrical components if you run a degraded wiring harness. To me, it's a critical component.

- My 500E runs noticeably better with the new harness - and strangely, even though I have been on the look-out for issues, I thought it ran fine on the old harness. But it's definitely more responsive with the new harness, and possibly is running a little cooler (always a good thing for our cars).

- My new "late" harness, the 124 440 20 06 part, was manufactured in Oct 10, and cost $540 + $32 freight from Parts.com --- I feel that I was over-charged for shipping, as the harness arrived in a -significantly- over-sized box, but that's a different story.....

- The removal of the old harness + installation of the new harness is a relatively simple job. Undo the battery. Unplug the various connectors, all easy to get to --- undo the various 5mm allen bolts holding the harness down, all easy to get to --- guide the harness out through the firewall --- install in reverse order. Hook the battery up again. It should be a 2-hour job, if you work efficiently and enjoy a beer or two along the way.

- The job will take much longer if you get the routing of the wiring confused or incorrect. I had the benefit of a knowledgeable owner of a pair of 500E's who was able to guide me through anything I was unsure of --- if you don't, then be sure to take a lot of photos before you remove the old harness.

- Pay particular attention to how the four looms are routed through the firewall (top-to-bottom: upper wiring harness, lower wiring harness, diagnostic plug loom, water hose), the routing of the upper harness underneath the passenger valve cover's breather hose, and the 180-degree bend that the upper wiring harness takes between the firewall and the top of the valve cover.

- There are a small handful of U-shaped wiring "holders" that guide parts of the harness and keep it snug against the engine --- these will break. You will need new ones, or zip ties. New factory Mercedes parts = the best, always.

- Keep a small container handy to put all of the bolts + brackets + washers that you remove in --- that way, if you think you're done with the installation of the new harness, but you have parts left in the container, then you know you missed something.....

- This can be a frustrating job. If it doesn't go 100% according to plan and starts to take a while, then your lower back will hurt a lot, your hands will hurt a lot, and you'll swear a lot (in German). Take a break every so often. I suggest you have a few pairs of rubber gloves handy. I went through 5 pairs.

- Have a shower, take your 500E for a blast down the nearest Interstate, and then drink at least six of your favourite beers after the job is done. You'll feel much better.

- In case you missed what I said above... take many many hi-res photos before you remove the old wiring harness. Very important.


Good luck!!

 

[askd9280]

Re: |Wiring Harness

Great Job.

I guess that proves that you can really use the "late" wiring harness on an early car?

 

[Silver Arrow]

Re: |Wiring Harness

Great Job.

I guess that proves that you can really use the "late" wiring harness on an early car?

Thanks - but....

.... early vs late harnesses do not align with 500E vs E500 / early vs facelift production.

The 1st harness type was used on 500E's built until a specific VIN - after that, the 2nd harness type was used --- this has nothing to do with whether or not the 500E in question was a facelift car.

However... I know for a fact that an early '92-built 500E will run absolutely perfectly with a late harness.

Also, I have complete pin-out diagrams for both harness types, as evidence --- not my work, though, so I will leave it for that individual to post the info.

 

[gerryvz]

Re: |Wiring Harness

Please post photos of your opened-up wiring harness to the forum. We'd like to see the condition of the wiring and of the ends of the connectors.

Thanks!

 

[askd9280]

Re: |Wiring Harness

Please post photos of your opened-up wiring harness to the forum. We'd like to see the condition of the wiring and of the ends of the connectors.

Thanks!

Some pics of my old harness.

 

[CHBinAsheville]

Re: |Wiring Harness

-Fingers crossed-

Anyone know of a DIY for installing a new replacement engine wiring harness......?

I'm hoping to do this install very soon, it would be a great help.

I had no trouble doing mine. Some areas were a tight fit but it is pretty much unplug old/plug in new. I plan on doing the bottom one next. I had more trouble replacing the spark plug wires, talk about a tight fit! I have been running the car without the new wiring harness being held down to the heat producing engine parts as I think this might extend the life of the new harness.
I took pictures and had a helper with me so if I forgot something she most of the time remembered. It really isn't that difficult.
For me I just don't feel as confident working on my Merc as with my other cars(SAAB/Volvo) but I find all of these so much easier to repair than rice burners with side ways sitting engines. The Japanese auto designers have found a way to get back at us, "Stupid Americans with BIG hands." Try doing a timing belt on a Nissan Maxima circa 1988.
Good luck and if you get stuck email me.
2wild4u@gmx.com

 

[CHBinAsheville]

Re: |Wiring Harness

Is the bottom harness more difficult than the top one? My car has 220k on it and I have been told to replace the voltage regulator at the same time. Any body know if this can be done without taking the alternator off?
Thanks,
Curt

 

[mb280sel1985]

Re: |Wiring Harness

Generally speaking, I'd do it from the ends of the tree branches and work toward the trunk, but that's just me.

It's probable that you're going to break some plastic clips and such, which are heat-baked and age-brittled. Make a note of the connectors/clips that you break, and you will probably want to look them up and put an order in to replace them. Be VERY careful on these pieces and you may well save a few of them and be able to re-use them. But there are going to be some plastic bits that just crack/crumble as you remove them. Just wanted you to be prepared for that....

Cheers,
Gerry

Are these "plastic bits" the only parts one needs to worry about?
How to order them - p/n?

Last time I ordered some clips for the air filter box from the dealer, they had to special order them from Germany. It was supposed to take 4-6 days but took almost 4 weeks! Since I have an appointment monday for the replacement - what to do..? Is it OK to put the plastic bits on later if they don't have it in stock - or just IS that sort of equipment in stock always?

 

[samiam44]

Re: |Wiring Harness

Is the bottom harness more difficult than the top one? My car has 220k on it and I have been told to replace the voltage regulator at the same time. Any body know if this can be done without taking the alternator off?
Thanks,
Curt

CURT, I've done it in my 420e. You'll need a 90 degree philips. I would suggest taking it out.. makes cleaning the whole area and alternator better. The rear bearing gets noisy and is $5-10 .. low hanging fruit. Is a little harder. If you replace a bearing.. bearingdirect.com and get the electric motor grade bearings(ABEC4?).

 

[J-Sauce]

Re: |Wiring Harness

Yes, the bottom harness is more difficult than the top. The hard part is routing the harness up behind the cylinder head. I had to remove my starter and exhaust downpipe. You will probably want to replace your starter at the same time if you have not already. Cheers!

 

[gsxr]

Re: |Wiring Harness

FYI, the starter harness routing is totally different between the 400E and 500E. No idea why the factory did that, but it's definitely not the same. And not a fun job if you don't have access to a lift.