TVGuide.com said Haddon began his career as a stage and live television actor in the late 1950s after he served as a Merchant Marine in WWII.
In addition to playing Ed, one of American TV's first gay characters, on "Mary Hartman, Mary Hartman," he also frequently appeared on "Dallas," "Trapper John, M.D.," "Knots Landing" and "Lou Grant." His last screen credit was the 1996 film "Infinity."
TVGuide.com said the actor died May 10.
Notable deaths of 2014 [PHOTOS]