wiring harness interchangability




Funny you should post this as I just changed my harness today (about a 2 hour job).
For USA M104 cars there are two wiring harnesses, the early harness, MB part 124 440 56 32 and a late harness, MB part 124 440 29 33. They are not really interchangeable and both are expensive, although the earlier harness seems to be a little cheaper.
The early version is often described as the "round" thermostat sensor plug version while the later version is known as the "square" thermostat sensor plug version. I believe the difference is because MB went to a single unit dual ECU and HAVC coolant sensor on later cars while the earlier version had two discrete sensors for each function.
While the number can, in theory, be determined from MB EPC look-up and from looking at the connectors, the most reliable method is to check for the part number on the harness itself (this is particularly important if your car is near the change-over point). This is located on a label attached to the harness where it passes behind the battery.
Upon closer inspection of my old harness, I was shocked that my car still ran given the condition of the insulation.
Hope this helps and good luck.
- FD
Last edited by Floobydust; May 15, 2011 at 10:22 AM. Reason: Fixed a few typos from posting at 1 AM . . .




