There is lots of information on re-wring the ETA on this and other forums. One thing that I have not seen mentioned in any of these discourses is separation of signal and power wires. If you look carefully at the original cable (if there is enough left of it) you will see that the smaller signal (e.g. switch and potentiometer) wires are twisted together in a bundle in the clockwise direction forming a center core whereas the power wires (along with some nylon "spacer" filaments) are twisted around this bundle in a counter clockwise direction. This was done to prevent crosstalk between the two circuits which operate at radically different power levels (signal: microamps or milliamps; power: amperes). I believe that failing to do this is one (of many) reason(s) why people can have trouble with re-wired parts.
There are two "methods" that people have posted for re-wiring the ETA. One is to replace the OEM wire entirely and the other is to re-insulate the OEM wiring with heat shrink tubing. I prefer the later method as it allows you to re-create the opposing spiral of the bundle. Removing the nylon spacers allows for the added thickness of the heat shrink. If you go for the former, I would recommend that you use a small gauge (such as 24 gauge)
stranded cable for the signal wires and multiple signal conductor larger (about 18 gauge) stranded wire for the power conductors. By noting the direction of twist in your cable, the signal power wires can then be oriented with the their twist in the opposite direction. You can even go with a hybrid configuration and use the cable for the signal and re-insulate that power wires. As with the other posts, be sure to protect and properly seal the repaired wiring.
Repaired ETAs, even if done perfectly, will be less reliable and less durable than OEM because they are by definition older than non-ecco junk units which are newer than 1998. But, I believe that a re-wired ETA, if done properly, can provide a service life that is mechanically limited (e.g., the gears, bushings, or potentiometers wear out) instead of prematurely limited by the wiring failure. It becomes a question, like many things on the W124, of time versus money.
- FD
ps - I added a pic of the wire bundle twist after heat shrink tubing was applied and a pic of the finished ETA. Note the armored cable protection
pss - One more thing. People usually uses silicon to "seal" the connections. Unless you use the correct type and prepare the surface properly, it is not reliable in this application. I use a true dielectric insulation sealer called Scotchkote that is designed to bond to both metal and wire insulation (including heat shrink) and create a water proof seal with 1000 volts/mil of dielectric strength. Coat the pins on the connector where the wires are soldered on and fill the channel where the wires pass through the ETA body to establish a seal. Then you can use silicon to glue everything else back together.
