Looks like this: http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CL0O6GWD1EM0R5BXV&year=1986&make=MB&model=300-SDL-001&category=P&part=Overload+Relay

On my 124 it is behind the battery under a loose cover. Not exactly sure on your 126.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html