Have a recent problem with W126 .. battery seemed weak ( 5 yr old ) so
replaced with new. Car sat for 4 days without being driven and get in it to
start... dead as a duck. Same thing has happened three times now.. if car
sits for longer than a day. I removed the positive cable and the auxilliary
attachment cable, main cable showed no pull or arching, but the auxilliary
cable arched severely... though maybe a relay was stuck, so continued to arc
probably 10-15 times. Finally the arc became just a small spark. I figure
that which ever relay was the problem had now reset???? What relays and
locations should I check?

Thanks for any advice.

Dave