A. William Wertz Jr., 49, a data communications representative for the Chesapeake and Potomac Telephone Co., died Wednesday at Washington Hospital Center. He lived in Kensington.

Born in Pittsburgh, Mr. Wertz attended Western High School here and Benjamin Franklin University. He joined C&P in 1951 as a splicer's helper, and later was a frameman, installer repairman, accounts manager and data communications representative.

From 1946 to 1948, he served in the Navy in Washington aboard the President's yacht, the U.S.S Williamsburg, and at the presidential retreat, Shangri-La, now Camp David.

Mr. Wertz was a scoutmaster and a member of the Alexander Graham Bell Chapter of the Telephone Pioneer of America. He belonged to St. Paul Methodist Church in Kensington.

He is survived by his wife, Peggy Anne, of the home; three sons, A. William III, of Silver Spring, and Kerry and Ed, both of the home; his mother, Flo Wertz, of Cottage City, Md., and five sisters, Jean Turpin, of Hyattsville, Janet Colenda, of Chicago, Marjory Byron, of Oxon Hill, Alice Lutz, of Hyattsville, and Pat W. Kemer, of Hillsdale, N.Y.

The family suggests that contributions be made to the Montgomery County Heart Association.