PeachParts Mercedes-Benz Forum - Thanks for the help

Last week, posted a thread about an intermittent problem with my '92 300SE. Every so often, it would just drop dead. Engine would crank but not start, A/C would blow, headlights would work, but virtually all other systems (close assist, windows, seats, mirrors, sunroof, central lock, etc.) were dead.

Yesterday, it pulled the same stunt again while test driving the car on another matter.

One of the suggestions in my previous thread was a possible failure in the ignition switch. I wiggled, jiggled and bumped the switch with no effect whatsoever.

I figured - OK - it's got to be a relay or bad connection somewhere, so I started in the trunk. Gently pounded on the relays, fuses and various modules found on the right-hand fender. BINGO - things start working again.

Resume the test and the bugger dies a second time. Back to the trunk - same procedure as before - no effect this time. Then I reach for the positive terminal on the battery. It's nice and tight. But there's a second stud on the terminal, to which is attached an 8 or 10 gauge wire. Wiggle this wire - everything comes on again. The stupid little 10mm nut that holds the wire on is not tight. Loose enough that a spark in the gap leaves some carbon - which doesn't conduct - and the car goes dead. Wiggle the wire - reestablish connection - for a time.

This explains how the car would drop dead just after hitting a bump or making a turn. In the process of working the gremlins out of the car and the battery isn't tied down tight. It moves, wire moves - spark and no conductivity. All the circuits that use that smaller wire for either their primary power or to power the signal circuits to trigger their primary power relays would go dead - but the car would still crank.

Lesson learned here - yet again - sometimes the simplest item is the solution to the problem.