My "new" 500SEL has been great so far, but I just encountered something troubling...

While driving along the freeway this evening, the engine seemed to cut out completely - I couldn't tell if it was even running at all. On the dash, the battery warning light came on.

I turned towards an exit, and six or seven seconds later (coasting at about 35mph) the battery light turned back off and the engine came back to life. No problems getting home after that.

I can figure out most problems with my diesel, but when it comes to this gasser I'm clueless. What happened? Alternator problem? (The headlights and radio never lost power, the battery works fine.) Fuel pump? (That wouldn't explain the warning light.) ...

Thanks...

__________________
'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

You need to check electrical connections. To begin with make sure that the connector on the back of the alternator is properly seated. Check for loose grounds and loose battery cables. It also wouldn't hurt to pull the voltage regulator from the alternator and make sure that there is still some brush length.

It also wouldn't hurt to do a voltage drop test between the alternator and battery. That would show up any bad or flaky connections.

If the problem comes back and stays a problem instead of fixing itself, check the battery voltage at a fast idle to see if the battery is charging, then go from there.

Good luck,

My uncles car used to do this... It was caused by the battery - starter lead touching the exhaust manifold and shorting out.

__________________
Ben

'85 500 SEL
'85 928S2
'88 560 SEC
'90 750i

If the head lamps didn't dim during this episode I would take a hard look at the ignition control module and fuel pump.
Mike