WITH AN EYE ON . . . : Diagnosis: Here’s a part that came <i> very </i> naturally to actor Barry Van Dyke

The last thing most kids want to do when they grow up is work 14-hour days with their dad. But Barry Van Dyke--who co-stars in his father Dick Van Dyke’s “Diagnosis Murder”--doesn’t mind at all.

“I’d work with him any time,” says Van Dyke, 42, from his Conejo Valley home. He adds that his dad, long labeled one of Hollywood’s nicest actors, is “the best to work with, very creative. He has a lot of integrity and he’ll work no matter what, including physical discomfort. He set a fine example. We’ve always talked about working together.”

On the CBS comedy-drama, where father and son act as father and son, Van Dyke plays police investigator Steve Sloan, who often helps his physician and mystery-solver dad, Dr. Mark Sloan, get out of hot water.

Producers thought it would be easier if they made the local police investigator Sloan’s son. “He doesn’t really want to arrest his meddling dad,” Van Dyke says, laughing. Of the Sloans’ relationship, he adds, “It’s an easy role for me to fall into. My dad pretty much plays himself. You’re seeing the real him. All that warmth and humanity really comes across. So I tend to play myself. So their relationship is pretty much ours.”

While Van Dyke’s siblings--one brother and two sisters--all considered careers in show business, he was the only one who took it seriously.

His father, well aware of the trappings of a fickle industry, advised his oldest son to wait.

“He wanted me to have my childhood,” says Van Dyke, who spent his youth in Mandeville Canyon and Encino. “He told me that if I still wanted to act after I graduated high school, then it would be OK.”

Even though the family moved to Los Angeles when he was 9 for “The Dick Van Dyke Show,” he never felt they were part of the show-business community. “My father didn’t travel in those circles. We were aware he was on TV and watched the show and knew it was successful, but we didn’t socialize with a lot of show-business types.”

Yet some of Van Dyke’s best memories include visits to the set of his father’s show. Watching Carl Reiner, Mary Tyler Moore and his father work together was “the greatest thing to see,” he recalls.

When his father worked on location, it became the family vacation. Trips to England and Hawaii are remembered fondly.

He acknowledges that, initially, his father’s name may have helped him get an agent, but it certainly didn’t help him get work. “There’s too much at stake for producers and casting directors to get you in on just a name,” Van Dyke says. Eventually, it comes down to: “You either perform or you don’t. You work or you don’t.”

And he worked, beginning as a “go-fer” on “The New Dick Van Dyke Show,” shot at his father’s small production studio in Arizona, where the elder Van Dyke had decided to “retire” before being persuaded to return to television.

Dick’s son held cue cards, ran the transportation department and basically gathered production experience. But he always wanted to be in front of the camera. Finally, he got his wish: He landed a job as an extra. More extra work and small parts followed.

Then he got really lucky. He landed a development deal with ABC. Although initially pigeonholed in comedy, his father’s milieu, Van Dyke found he had more of an affinity for action-adventure. Regular series work followed, including “Battlestar Gallactica” and “Airwolf.”

And Van Dyke may be following in his father’s footsteps in more ways than one: He’s got his own family dynasty in the works. During his first foray into “entertainment,” Van Dyke took tickets at a local movie theater, where he met his wife Mary, when they were both 16. They married seven years later, when Van Dyke was working as an extra. The Van Dykes have four children: Carey, 18; Shane, 14; Wes, 9, and Taryn, 7.

It seems his kids are eager to work with their dad too. The Van Dyke family, who surf and dirt-bike together, is hoping to start its own production company soon.

“Diagnosis Murder” airs Fridays at 8 p.m. on CBS.