A WEAK HEART was a subject on the mind of L. Frank Baum, who suffered from one, and that may be why he created the Tin Woodman, the man "without a heart." Jack Haley, who died Wednesday, brought the Tin Woodman to life perfectly, though as he lamented to Dorothy: "Bank on my chest if you think I'm perfect." Dorothy called him the Tin Man, instead of the Tin Woodman in the movie of "The Wizard of Oz," as if to emphasize the fact that a man of tin would ordinarily be considered a robot, nonhuman. But Mr. Haley's Tin Man proved how human tin could be; and as for lacking a heart, it was all in his head.

Of course, that was the theme of the "Wizard of Oz," the theme of self-reliance, everyone on a quest for what he already possessed. Of Dorothy's three companions, the Tin Man was probably the least entertaining - neither as jumpy as the lion nor as supple as the scarecrow. Yet what he felt he lacked, what he wished for, mattered most to his audience, who would take a heart over courage or a brain any day. Of the three he also needed the most help from others, as he was ready to rust at the drop of a tear.

Perhaps for that he was especially endearing. And only an actor as accomplished and patently kind as Mr. Haley could have pulled off the part without seeming merely a clanging galvanized dope. He could not make you laugh the way Bert Lahr could, or dazzle you with footwork like Ray Bolger, yet he won the hearts of children as much as the others because his Tin Man was like a toy, a favorite toy, a gentle spokesman for the world of feeling in all things. As the wizard told him when he handed him a heart-shaped watch: "A heart's not judged by how much you love, but by how much you are loved by others." So it was for Jack Haley.