W140 Electrical Problems
Friend's '93 500SEL, with 142K miles, recently had a factory remanufactured transmission installed. The transmission R&R was uneventful. The day following the transmission service the starter self-activated while the vehicle was traveling at 60 mph. The vehicle was returned to the shop, where the wiring harness for the starter and alternator was found to have loss of insulation. The harness and starter were replaced. The day following the harness replacement the charging system warning light illuminated - maximum alternator output was 11.8 volts, so the alternator was replaced. Today, 10 miles after alternator replacement, the instrument cluster fuse (20 amp) blows everytime the turn signal or hazard warning switches are activated. According to the VMI, the engine compartment wiring harnesses were replaced at 63K miles. Any idea as to what the problem might be. Is there another harness that needs to be inspected? The vehicle was free of electrical gremlins before the transmission replacement and the repair shop is known to reputable... the four small gauge copper wires in the starter/alternator wiring harness were green in appearance and lacking most of their insulation.
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