Can anyone help me ID what the wires in this connector lead to?

This is p/n/ 1235400369 located on the firewall side on the expansion coolant tank.

The purple and yellowish wires on the far right are ground. I think the yellow wire in the middle is to the starter - it goes in that direction along with the main positive lead from the battery.

The other two wires (on the left end) go into the firewall at the point in pic#2. What do these connect to?

Attached Thumbnails

   

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

It looks like the connection from the battery to alternator via the starter. If it is, the glow plugs are also connected there.

And ground connections are generally brown, not yellow or purple. And those wires could be white and red, which is more likely faded into the colors you perceive.

Could be hot, voltage-wise, at all times. Check it out. Take care.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

I do think that they have faded, and were white and maybe red.

The middle one feeds current to the whole car....disconnect this and no power to anything.

Disconnect the purple wire and no starter engagement. Disconnect the other one and no apparent effect.
I cant disconnect the other ones on the right - too melted.

What would cause these wires to melt? My #8 fuse also runs hot with the blower motor on in this car. Not sure if it's related or not.

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

Here's a link to the Electrical schematics for your car. Hard to say looking at it, cuz it looks like everything is supposed to be connected at the starter. You'll probably be best off just disconnecting what you can, then doing continuity checks to see if they go where you think they do. That junction has alot of current going through it. If you develop a bad connection it acts like a resistor and generates heat. That could be what led to the melting. If you need to, cut the wires and solder them together into a copper lug (see a Noble catalog for source) and wire it back to the junction box. You can probably find a junction box in a pick-n-pull.

81_240.pdf - 3.06MB

Let me know what you find out. The schematics should help alot.

__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

need schematic

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'84 300SD sold
124.128

If you are using old plastic bodied fuses, this may cause your melting.
Clean and polish fuse box contacts and replace the fuses with new ceramic bodied fuses.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

nahh I don't think those wires go through a fuse. certainly not one of the fuses in the fuse tray.
the melted wire looks to be the main power lead to the starter solenoid, or the charge lead from the alternator. (my SD has an extra wire there, so not sure exactly)

Yes, I don't think these go through any fuse. Last night I confirmed that I am getting inadequite voltage from the alt, so it must be the 4 strand wire to the alt/VR./Starter in the schematic micalk generously provided (THANKS!!!), my FSM is unreadable.

I read another post where someone had some melting there and lost alt recharging, so I am heading to the dealer to get a starter/alt wiring harness and new connector, and will see if it melts again. Hopefully this is just due to the poor thermal shielding I have read MB used until the mid-90's on these harnesses. Once it meltede a bit, it started shorting and got hotter and hotter and melted more and more....at least that is what I am hoping.

Will report back once I get the new harness in place!

thanks again everyone!

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

hey, many have upgraded that wire to #4 or larger to support a 120A alternator.
sounds like a plan to me...

A trip to the dealer$hip was very informative.

The wire from the alt is the single one that leads to the center pole of the 3-pole connector. that wire seems fine - i am hoping the low voltage is due to the shorting at the 3-pole connector preventing the current from making back to the battery.

The 4 strand wire is the harness for the ACC. It also connects to the drier, compressor, and the fuse box. Not indicated in the schematic, but it must be #8.

Cost of the harness alone (no connector included) = $875

So I called a salvage yard and they will sell me both the harness and connector for $100.

So I will head there later this week and get a harness. I imagine it will be a bit of a bear to rewire that. Hopefully I can get to all the places I need with the dash still in place, but we will see.

Soooo...that part is one of those things that MB contracts to unicorns, and replacement with a new harness is almost not worth the value of the car - considering that I am not sure why it melted in the first place, and whether the replacement will do the same!

Has anyone here replaced this harness before? Haven't found any links in searches.

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

First off, a short has to go between two circuits not intended to be connected, i.e., 12V and ground. If two wires belong to the same circuit, and are supposed to be connected to each other, then they are by definition not really shorting. On the other hand, a bad connection could lead to an open circuit, or as I described, low voltage due to a resistive voltage drop at the bad junction. Make sure you understand what your problem is and what the solution is before replacing parts.

Where are you seeing a low voltage? Especially if it is coming part of the battery circuit you are going to want to look around for bad connections. Like I said before, a bad connection will cause resistance, and the more current dropped across a resistance the higher the voltage drop. The three pole connector may be designed to short those wires together - Battery, alternator, starter should all be connected directly to each other. If there's another short to something, you haven't really described it to us.

Before forking out for a wire harness, you could try making your own. At the very least, make up a set of wires to test your system. You could do it for about $5 in parts and wire. Or patch up the wires you have making sure you have good solid connections. It can look ugly as sin as long as it works well enough to show you if you've resolved the source of the problem. If the test harness solves your problem, install the new harness. If the test harness burns up, you haven't lost much.

You really need to look at this circuit. If the alternator is shorting to something, it's the same as the battery shorting to something, and I'd expect you to be having dead battery problems. You've never really described the problems you are having. It might help us to give you advice on where to look.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

Yeah I wouldn't bother replacing the harness yet. The wires on the terminal on the left look funky, the others look ok. I'd take the funky wires and cut off the ring spades, strip the insulation and crimp new heavy duty ring spades on and see if that cures it.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Ok, I will follow your advice re resoldering the spade connectors.

Unfortunately, I only read it after I bought a wiring harness from a junkyard. They couldn't separate the $875 wire from the rest, so they sold me the whole thing. t was actually worth the price, just to see him remove the dash and wire by wire unplug the harness to get it free.

The problems I am having are these...
One of the cube relays above the DS wheel failed and had to be replaced - AC was not getting power.

Replacing the relay restored AC power, but the #8 fuse (compressor/blower) runs REALLY hot. It's the only fuse on the block that runs hot.

Running a tire pump through the cigar lighter makes that 3-pole junction box hot enough to melt. So does running the AC, though it may run that hot with the AC off....not sure about that though.

Voltage at the battery with the car running is just over 12V

Leaving a car door open for a few hours to overnight will drain the battery so the car won't start.

Sometimes the car will start, drive somewhere, then have too little power to turn the starter on the return trip.

This weekend, left the house with a full battery, drove out of town 60 miles, and the battery died. shifting got weird, windows and antenna barely moved, and no crank. Had to get get towed home
Battery read 9% on the home charger.

I now know this is because the battery is not recharging. I am recharging the battery every night with a charger to prevent stranding dear wife.

the 3-pole conenctor does appear to short the left and middle terminals and provide a junction for the 2 wires at the third.

Finally, the tach has always been flaky - flatlinees, then swings wildly, then works for a while, then stops working.

Oh yeah, I will also be checking the ground points

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

I hope you didn't pay $800 for the harness! Unless you had a short in the harness and it caught fire and burned up, taking other wires with it, I can't see replacing a harness. When you have a bad connection, be it from a wire to a crimp terminal, a terminal to a terminal block, or between 2 terminals, the bad connection has high resistance and gets hot. In extreme cases a fire ensues if it gets hot enough and there is flammable material near it.
Sounds like you have chaging problems also.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Nope but I got my money's worth seeing how to remove the dash and where all the vacuum pods and wires run - kinda like watching a dissection on a corpse that wasn't mine

The mint Becker Mexico I got for a song was also a plus!

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT