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Discussion Starter #1 (Edited)
Hi, I recently bought a W163 ML 270 cdi 2003 model. It is in reasonably good condition, well equipped, black with black leather, with 254K km on the clock. It need new brakes front and rear, one new rear spring (got a set of spring/shocks at a very nice price!), outer steering joints both sides, and front upper right side carrier joint (chicken bone), as well as a polishing of the headlights. I took out the battery for charging, and noticed some serious corrosion on two cables attached to the wall behind the battery, see photos.
Can someone please tell me where these cables are routed, and what they feed? Are they long?
Are they attached directly to components, or do they have similar connectors at the other end, as those corroded?
A serious 'flu attack, and the weather, has prevented me from doing much practical investigaton into the problem, so I hope for help from some expert.

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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Hard to see in the photo the extent of the corrosion on those cables.
Perhaps use some electrical contact cleaner and small fine wire brush to clean off the surface and then take a closer look to see the extent of the corrosion. It's the +ve end so I would use a bit of petroleum jelly and coat to prevent further corrosion, if its not to bad. Usually, it's an indicator of overcharging.

Read here - Firewall Battery Terminal Question
One example.


Try using the search feature on this forum - Wealth of information.


Screen Shot 2020-01-18 at 9.23.25 PM.png
 

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Discussion Starter #3
Thank you for the link, khomer2. It seems that there weren't any good solutions to a problem known to many owners. I'll make new cables, or maybe just fit new connectors. But, if the bolt in the firewall is not connected to any electrical point on the other side of the wall, and just acts as a connector for two cables, I think that I'll make a new and better, closed connection elsewhere, or maybe a long cable that eliminates any connections.
The designer of that connecting bolt must have experienced a serious brainfart! :rolleyes:
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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Thank you for the link, khomer2. It seems that there weren't any good solutions to a problem known to many owners. I'll make new cables, or maybe just fit new connectors. But, if the bolt in the firewall is not connected to any electrical point on the other side of the wall, and just acts as a connector for two cables, I think that I'll make a new and better, closed connection elsewhere, or maybe a long cable that eliminates any connections.
The designer of that connecting bolt must have experienced a serious brainfart!
:rolleyes:
We have 2 w163s, 99 & 02. This is a known issue? Where did you find this info that says this is a known issue?
Personally, never heard of it, never read about it.

Really, a new and better connection? ATPTY
but ummm, I don't agree this was a brainfart (in this case)

Here - another freebie for your reading enjoyment. :)
More reading - Positive 12 volt connection on firewall

As I stated, there is a WEALTH of information on these forums from many great members - take the time to search, read and enjoy. :)
 

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Discussion Starter #5 (Edited)
I have searched, and read, several threads about the same problem. And since you have provided links to similar problems, it obviously is a known issue. According to member Witek_M, this connection was introduced 9/2000, which means only your '02 model may see the problem. Perhaps you should take a look behind your battery? Besides, overcharging wil not cause that problem, that would have made corrosion present at the battery pole connectors. The placement of the connector in the firewall, sitting behind a battery without provision for closed ventilation of acidic vapors to the exterior, is the reason. Thus, brainfart! :) Climatic conditions may of course also contribute to the corrosion.

I wish someone could tell me if the bolt is connected to an electrical point behind the firewall, or if it just is a connecting point for two cables? From the parts list, it looks like a separate piece, acting only as a connection.
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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I have searched, and read, several threads about the same problem. And since you have provided links to similar problems, it obviously is a known issue. According to member Witek_M, this connection was introduced 9/2000, which means only your '02 model may see the problem. Perhaps you should take a look behind your battery? Besides, overcharging will not cause that problem, that would have made corrosion present at the battery pole connectors. The placement of the connector in the firewall, sitting behind a battery without provision for closed ventilation of acidic vapors to the exterior, is the reason. Thus, brainfart! :) Climatic conditions may of course also contribute to the corrosion.

I wish someone could tell me if the bolt is connected to an electrical point behind the firewall, or if it just is a connecting point for two cables? From the parts list, it looks like a separate piece, acting only as a connection.
Avvan,

I have. Thank you, for asking. zero issues.
I maintain and work on our MBs as well as the neighbours in our area. No expert but learned enough and learning more.... ;)

Screen Shot 2020-01-18 at 11.24.05 PM.png

As for +ve terminal corrosion comments, I disagree. You said yourself, you recently purchased this suv. How do we know whether the seller did or did not "cleaned up the B terminals" and under the hood anything that's visible... made it all spiffy for the sale? (just say'n...)

As for your idea of re-inventing a new cable... as I stated....ATPTY.
Keep us posted ;)
 

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Discussion Starter #7
Does your E50 has a battery compartment under the passenger seat? If so, it has a battery with external ventilation to avoid corrosion, and potentially explosive vapors. What does ATPTY stand for?
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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Does your E50 has a battery compartment under the passenger seat? If so, it has a battery with external ventilation to avoid corrosion, and potentally explosive vapors. What does ATPTY stand for?
Well of course, that's why I never use a 'conventional battery' inside ANY vehicle. It's called an AGM battery (or gel cells).
What is your point going off-topic?

ATPTY= All the power to you
 

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Your photo shows Part number 163 546 01 72 or Cable Harness Mounting Nut which attaches to 1635460141 Cable connector. I think it is a splice that provides a splice in the Positive cable so power can pass through the fire wall to the cabin fuse box in the foot well.

Unbolt the cables, clean with a wire brush or contact cleaner. If they look good put some conductive anti oxidation paste on them and reassemble.
If bad snip off the lugs and crimp on new ones. I too have not read about them causing many issues, a lot of other items tend to be more of an issue AAM
failure, Rear drive shaft support bearing, mount mounts.
 

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Discussion Starter #11
I think it is a splice that provides a splice in the Positive cable so power can pass through the fire wall to the cabin fuse box in the foot well.
Yes, I would think so too, but in the EPC, there is no indication of a connection to the other side of the wall. But, I found this on the net, where a cable is attached to the connector on the inside. The problem is close to a solution!

 

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Earlier mls had no cabin fuse box. If I am remembering correctly the cable from battery to engine fuse box runs along the firewall. When they added the cabin fuse box. Thought was in effect cut the cable put lugs on it come up with a junction box to safely run it through the firewall and tee it off to the cabin fuse box.
Bet when you undo the engine compartment connections I bet the lugs under the nut will be in good shape.

Part of the corrosion could be splash over of windshield washer fluid?
 

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Discussion Starter #14
wallyo, I hope you are right about the shape of the connections, and there is definitely a possibility that windshield washer fluid could be a reason for corrosion. :) I'll report back when I have fixed it.
Last night I found a youtube movie, focussing on the modifications to the ML as of 09/2000. If you spool 8min 34sec into that movie, there is a reference to the new fuse box #2, and the feed to the fuse box from the connector in the firwall is shown.
 

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Avvan

Great video find. Very informative, so much so that Moderator how about a new Sticky entitled
"Videos Repair and Information"?

We have Photos of your Ml, documents, part pics but nothing covering videos only.
 
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