Mercedes W123 Fuel sender removal, cleaning, cluster and wiring test and finally actually fixing it.

Specifically this video is of a 1982 W123 300D, Many other cars near this era used the same or similar sending unit, my w116 did, w126 do for sure, w124 were similar, if nothing else this should give you a vague idea where to go to remove, and hopefully repair your sending unit, and test your cluster and wiring to the sending unit.

My sender had been on the fritz for quite some time. Likely caused by a fillup of bad diesel a couple years ago I believe was algae contaminated.

In this video we remove the sender, figure out how to disassemble it, clean it up, reassemble it, test it (still doesn't work), test the wiring and cluster using a very simple jumper wire method, then tear the sending unit back apart and discover the actual fix, then show you the functional sending unit.

A gentle touch is needed with these tiny wires and delicate pieces.

Saved myself over $180 buying a new sender by fixing the OE unit.

Key things in video:

0:00 Introduction
0:55 Removing first aid box
1:24 Discussion on tools to remove sending unit (46mm socket, 1 13/16”, possibly large crescent wrench, pipe wrench or channel locks)
2:00 Cracking loose the sending unit
2:25 Let the diesel drain back into the tank. Don't be like me.
3:10 I figure out you can unscrew the little nub on the end to disassemble it. Carnage from inside follows immediately.
4:10 Broke a wire. Soldered it back on.
4:40 Plastic end cap removable to ease reassembly!
6:07 Does it work? No.
6:20 Testing cluster and wiring by jumping the pins on the connector under the first aid tray. Key has to be on for this test.
7:52 Video isn't actually over. Explanation of function and what I had to do to actually get this working again. Most likely I popped the wire out of place while cleaning all that grunge off
8:30 Roughly enhanced picture and drawn arrows of what is where and how it needs to be. My lens was getting less and less happy and I couldn't keep it focused well to get video of actually putting the wire back in place
9:38 Testing it now that the wires are running inbetween the contacts like they are meant to be



Affiliate Links:
Here are some links to products we used in this video on amazon in case you want to try this:

Soldering iron: https://amzn.to/2AZXYcs
Contact cleaner: https://amzn.to/2B0PKRk

Replacement sender should yours be beyond repair: https://amzn.to/2KWzqsN (2 Year warranty)