Pat Harrington Jr., the veteran comic actor who won an Emmy Award for playing nosy but endearing apartment building super Dwayne Schneider in the long-running TV situation comedy One Day at a Time, died at the age of 86, his daughter said on Thursday.

Tresa Harrington said in a statement on her Facebook page that Harrington died on Wednesday evening.

She did not give a cause of death but had written in early December that he was suffering from Alzheimer's disease and was in declining health after a fall and a brain hemorrhage.

"My heart is broken to pieces and I will cry and cry until I just won't," Tresa Harrington wrote.

Pat Harrington Jr.

Pat Harrington Jr. as building superintendent Dwayne Schneider. (Facebook)

The actor's longtime manager, Phil Brock, described Harrington as "a gracious human being who will always be remembered for his portrayals of the human condition."

"Pat had the ability to bring laughter and kindness to any role. The twinkle in his Irish eyes let you know that you were in on the joke," Brock said in a statement.

In 1975, Harrington was cast as the faux suave Schneider in the CBS situation comedy that followed the lives of newly divorced mother Ann Romano, played by perky Bonnie Franklin, and her teenage daughters, portrayed by Valerie Bertinelli and Mackenzie Phillips.

Harrington won Golden Globe and Emmy for role

The series ran for nine years until 1984, the year Harrington won an Emmy - the top U.S. TV honour - for best supporting actor.

He also won a Golden Globe Award for best supporting actor in 1981.

"He turned out to be the comic strength of the show," famed TV producer Norman Lear, who developed One Day at a Time, told the Archive of American Television.

The New York-born son of a vaudevillian, Harrington got his first break in show business in the 1950s when comedian Jonathan Winters discovered him performing a goofy comic character named Guido Panzini for some friends.

Harrington brought the character to popular TV shows hosted by Steve Allen and Jack Paar.

He then studied acting alongside Jack Nicholson and other future stars, and landed guest roles and regular parts on a variety of TV programs.

He also appeared in numerous movies, including Easy Come, Easy Go in 1967 starring Elvis Presley.

One Day at a Time broke ground

One Day at a Time was a departure from many of the family sitcoms that had populated American television since the 1950s.

It presented dramatic situations involving Franklin's character struggling to find happiness as a single mother in Indianapolis.

There was drama behind the scenes as well, with Phillips battling drug abuse and at one point being tossed off the show.

Harrington's character, who always had a crush on Franklin's character and became virtually part of the family, saw himself as a lady's man and often entered Romano's apartment unannounced using his superintendent's master keys and snooping around.

Schneider, sporting a smarmy pencil mustache, invariably was clad in a white T-shirt, denim vest and tool belt.

At a televised cast reunion two decades after the show ended, Phillips told Harrington: "Schneider was very popular. And, you know, you became like a sex symbol for women over 40. You're aware of that, right?"

"It was such, such fun," Harrington said of the series. "Here's what you had: You had a middle-aged single man who was lonesome. Look what landed in his lap: a ready-made family. A gorgeous woman that I figured I could hit on and two kids who needed to be straightened out."