Mercedes R129 6 cylinder Engine Wiring Harness Replacement
I recently replaced the harness in my ’94 SL320, the reasons for doing it were easy. I had started to notice some bare wires in areas under the hood and felt it was about time. I had found a diy link on one of the other MB resource forums and thought hey why not. My previous mechanical experience is not overwhelming and I would class my ability as intermideate to advanced. (Previous fun ride was a 1972 TR6). BTW that cars harness never looked like this. Here is the link:
http://www.peachparts.com/Wikka/M104WireHarness
Also from this link I purchased my harness cost $550.00 time spent about 2 hours and 20 min. start to finish. BTW this price was the cheapest I found (free ship). The link shows you a similar MB sedan 6cyl install the difference between this and an SL is simple and also requires more time and care. First our battery is in the trunk, but the harness starts in the same area in front of the right side A pillar under hood. Remove the plastic cover and find the start point, then as you look at the car from left to right (you are at the front of the car) you will see where the harness exits the firewall. There is a small metal panel there that is topped by the weather strip closest to the engine, it is only held on by 2 bolts remove the bolts and lift off the weather strip then rotate the panel left to right (there is a cable that passes thru the panel and we don’t want to disconnect it) you will see the plastic mount that the harness runs thru flip it up (it is also connected by a flexy strip so you don’t lose it)and remove the harness start at the multi plug attachment. While I was in here I also opened up my cabin air filter and vacuumed out a whole pile of accumulated crap, I will order a new filter soon but my car came north from the Carolina’s and it was evident from the amount of pine needles stuck in there. As you begin to replace the harness move slowly the link is correct that the plugs only have one home but some are easier to work than others and these cars build up tremendous under hood heat so take care around vacuum hoses (personal experience) as they are brittle. Honestly I was 20 minutes in and said what the hell am I doing but if you move methodically you can accomplish this task easily. And save yourself at least $1k in labor charges dealer. I broke one vacuum hose at the very front of the engine (it is a 1/8” outside diameter emission hose available at Autozone $4.99 for 3’). I connected the battery fired it up and it drove like a champ no warning lights and no annoying skips at full throttle. I don’t know how easy an SL500 would be (less underhood room) but this is an easily accomplished job if you are patient and have the proper tools. Tools required range from screwdrivers to regular and torx sockets always have an extended magnetic tool for bolts that decide to escape and have at it. The biggest difficulty was reaching under the intake runners to hook up a connection (my hands are a little to big for this area). But other than that everything was as described.
Best Regards,
Keith