Does anyone know the real deal on w140 wiring harness??

I have heard from several independent mechanics that these should be replaced on my 1995 s420 because of factory defects. My dealer refused to change my harness (which is still under warranty) because they assert that their visual inspection did not result in a reason to change it. One of my mechanic friends said that I should have it changed because a defective one could fry the controller modules.

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jimSF