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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Discussion Starter #1 (Edited)
Good Afternoon.
I generally peruse the W107 board due to the lack of issues with my 300E, but I have come up on one that has my head scratching.
I need the central door lock vacuum pump to run, but so far as I can tell, there is no (+) to the pump. I get a good ground though.
Also in troubleshooting the issue, I get a good ground coming from the 3 switches, but no positive, leading me to believe that there is something in the X30 block.
I also checked the Fuse, and that is fine.
I do not have too many things hooked up there, but I unplugged them all, tested the positive, and negative leads, and they seem to check out.
My question is:
Is there a plug other than the X30 that would lead to this behavior? I mean somewhere in between the X30 and the pump is there a connection that could become corroded?
Also to note is that my drivers side puddle light will not go on, even though the passenger side one works fine. Might be related, then, it might not be.
Any help will be hugely appreciated.
BTW, I did a search and found nothing that really matched.
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
One or two other 124 owners have reported a problem with the large splice that joins 5 or 6 red wires together just forward of the pump. There is definitely a thread on it and I may have posted a pic of the splice. I cut apart a junk central locking systme harness (mouse damage) and found the splice.
As I recall you access the pump, look for the harness branch with the part number printed on it, and follow that branch forward less than a foot to the splice.
One member removed his passenger side front seat to get to the splice but I don't think that was totally necessary. Removing the door sill plate and bending the carpeting forward should be sufficient.
IIRC the brown wire also has a big splice in that area of the locking system harness.
 

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Registered
1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Discussion Starter #3
Thanks. I will look for it tomorrow, and report back.
:thumbsup:
 

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89 300E; 00 E320
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2,515 Posts
The black/yellow wire (hot in run and start) from Fuse A and red/white wire (hot all times) from Fuse C going into X30 should both be hot. The red/white wires leaving X30 goes to X48 then to the supply pump M14/2. And the black/yellow hot wire leaving X30 goes directly to the pump.

I believe X48 is the connection that augapfel is speaking about.

Also red/white hot wires in this circuit go into both front doors, and therein sometimes lies the problem with wires becoming weak.

X48F Right rear door sill area

F1 Fuse and relay box Left side of component compartment 231-4

Fuse A and Fuse C


Wiring Diagram:

Central Locking System 146

X30 Connector, block for optional electrical equipment Behind driver’s left kickpanel 234-2
 

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Registered
1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
Joined
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142 Posts
Discussion Starter #6
Now this makes sense. When I got the car, the PO had never resolved an issue where there was a leak in that area, and the carpet would get soaking wet. I finally figured out that the door was out about 1/16" so when I set the door in flush with the body the leak stopped, and it has been bone dry.
With that area flooding, of course there will be corrosion there, and a break.
I will check it out today, and you guys are outstanding...
:bowdown:
 

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1976 450 SLC. (working, in need of paint)/1987 300E/1989 635 CSI/2004 Honda Element (appliance)
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142 Posts
Discussion Starter #7
Thanks! It worked.
I thought that the splice would be a connector block, but it was just 4 cables sort of put together. It was exactly where it was supposed to be, and I think that this had happened in a long ago past as they had already messed with it.
Now, I have a working central locking system, and all the doors work great, trunk works great. One less thing to worry about.
:thumbsup:
 

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New Project: 1994 E420-------1986 300E (SOLD)
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53 Posts
I remember having this same issue years ago on my 1986 300E, and found that distribution point (x48F). I did a write up on peachparts.com.

Now I have a 1994 E420, with the same issue, but cannot find the x48F distribution point. It is definitely not in that area. I have moved up to the fromt passenger footwell (removed the seats and carpet, and is not there either. I am sooooo frustrated trying to find it.
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
So much changed between the early 124s and the later ones. I think 1990 was the introduction year for the convenience module that allowed the neat "close all the windows and the sunroof using the key in the lock cylinder" feature but that brought complexities.

I have a 90 TE 4Matic parts car. Maybe it's time to dig into that harness...
 
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