See if you can peel back the protective sheath on some of the wiring to take a look at the insulation. It should then be obvious. If the insulation is cracked and flaking and you see bare copper wire, then I recommend changing the wiring harness with a replacement. You can get one for $650 from PartsShop at the top of this page. Mine was more expensive since it's a later production model.
95 E320 Cabriolet, 131K