71-24-01 MCDONNELL DOUGLAS: Amdt. 39-1336 as amended by Amendment 39-1413. Applies to all DC-9 Series (except All-freighter) certified in all categories. \n\n\tCompliance required within the next 100 hours' time in service after the effective date of this AD, unless already accomplished. \n\n\tTo prevent failure of the cabin ceiling lights rotary switch and circuit, accomplish the following: \n\n\tModify the ceiling light control wiring in accordance with either Douglas Aircraft Company Alert Service Bulletin A33-55, dated October 8, 1971, or later FAA-approved revisions, or Douglas Aircraft Company Service Bulletin No. 33-56, dated February 25, 1972, or later FAA-approved revisions, or other modification approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\n\tAmendment 39-1336 was effective November 20, 1971. \n\n\tThis amendment 39-1413 is effective March 24, 1972.