400e No Electrical Power - PeachParts Mercedes-Benz Forum

mapkos · #1 11-14-2009, 10:22 AM

My 1992 400e probably has the worn wiring harness problem. Periodically, it will slip into limp home mode, which can be cured by turning off the car and restarting it. Last night, while sitting at a stop light, it started the uneven idling and I turned off the car and restarted it, but when restarted it still had the uneven idle. I turned it off and tried to restart and everything went black. No power at all. No warning lights nothing in the middle of pretty heavy traffic. I had to sit at the light without any warning lights, or lights of any kind. You can imagine all of the cussing and honking that was directed at me. I had it towed to a garage and waiting for it to open on Monday, but I'm wondering if it is something relatively simple, like a fuse or some connection between the battery and alternator. The battery is less than 3 months old. Anyone have any ideas?

Thank you.

Legoinsaniac · #2 11-14-2009, 02:59 PM

I had the exact symptoms (luckily not in heavy traffic), and yes, it was the wiring harness. Regrettably it's not going to just be something little like a fuse. It's a fairly expensive part, but it's very easy to install yourself, so you could save a little money with DIY. Also, there is an upper and lower harness. The upper is the one that runs to all the fuel injectors and such, while the lower one goes to the alternator. Just do 'em both at the same time. The lower one is only $100-ish. You will be AMAZED at how degraded and cracked the wire insulation is... I couldn't believe my car was running at all...

mapkos · #3 11-14-2009, 07:19 PM

Thanks for the post. I'm a little embarrassed, I had the battery checked and it was fully charged and the guy suggested that I double check the connections. I stopped by my local auto parts store and bought a battery cleaning kit that had a wire brush, cleaning fluid and sealer. The battery connections and cables looked okay to me, but I cleaned everything and sealed the connections and it fired right up. Never have run into this before.

As it relates to the wiring harness; I was thinking about doing it myself, but did not realize there are two. You mentioned the lower one was $100. How much was the upper harness?

Thanks again.

92 400E - 108,000 Miles