Date registered: May 2009
Vehicle: Ferguson TED-20 1956, Mercedes-Benz 220 S 1963, Valmet 502 1973, Mercedes-Benz S 500c 1996
Mentioned: 0 Post(s)
Quoted: 5 Post(s)
I just replaced the harness in my S500 -96... Since yours is a Diesel, and an early one, I assume it's still the one with the mechanical injector pump?
If so, those engines really doesn't require that much working electricity to operate (if any, but then again, just assuming)
Hopefully, from what I can google it seems that the 300 SD have a big cable harness going from the engine, via the firewall, to the black coffinbox, if you just check, you might have a big nice connector there which can make the change/removal of the harness quite easy.
Eitherway, it is possible to rebuild the harness by yourself, and depending on how complex it is on the diesel (hopefully less than the V8) it may be quite doable!
I also belive it is possible to purchase the connectors needed seperatly from mercedes, that way you wont have problems with connecting a new wire, to the old wire still on the connector. Some plugs mightr be possible to dissasemble, and some not... So I guess you'll have at least a few hours of fun from this!
Make sure you have a good wireing diagram diagram though, it will come in handy!
If you do it by yourself, make sure you do all the wires. Even if some look good, they're about the same age, and been in the same environment as the ones gone bad. If removing the harness is anything like on the 500, you really dont want to do it to many times (take it from someone who knows :-))
Personally I went for a brand new harness. A bit insane due to the cost (€1800, probably different for the Diesel, and checking doesnt cost!), but should it fail, I have someone else to blame!
Also, from what I seen on forums the insulation sort of disintegrates on the harnesses, but that was not the case for me, it had fatigued were it goes from the firewall to the engine (i.e where it moves the most). That was actually the main reason I went for a new one.
Anyway, hop this proves at least slightly helpfull for you, and good luyck!