I'm really surprised that the harness is discontinued. Is your dealer parts person pretty sharp? I'm surprised because everything I've ordered for my '95 coupe or the wife's C280 has been available, and the engine harness is a pretty popular item. It's tricky without the VIN but I'm coming up with A202 540 38 32 as a part number for the '95 C220 harness. I can check with my dealer if you want. I've seen a lot of people have luck rebuilding the harness, and if you're real handy it's an option. The wiring does need replaced; re-insulating the original wires I don't believe is feasible.

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1983 380SL
1995 C280
1995 S500 coupe
1990 Mazda Miata
2004 Suzuki Hayabusa