A tale of two Stratfords -- and their struggles; American Shakespeare Festival opener is a success, but only partial; Henry IV, Part 1; Play by William Shakespeare. Starring Christopher Walken, Chris Sarandon, Roy Dotrice. Directed by Peter Coe for the American Shakespeare Theater.

One wants this ''Henry IV'' to succeed, because one wants the American Shakespeare Theater to survive.

This fine institution has faced hard times recently, with money problems and artistic crises reportedly bringing it close to collapse. Even last year's ''Othello,'' with James Earl Jones and Christopher Plummer, which moved to Broadway for a deservedly acclaimed run, couldn't turn things completely around. A rousing 1982 summer season would presumably smooth its rocky road to a healthy future.

So what's the verdict on ''Henry IV,'' which continues through Aug. 1, after which ''Hamlet'' takes over the stage?

It certainly fulfills the apparent goal of artistic director Peter Coe to mount Shakespeare in true Elizabethan style, with major actors in the major roles. Presented in a single setting with no-nonsense costumes, the production is basic to the point of severity; a dramatic lighting design is the only distinctly modern touch. And the leading performers are all notable. The contending Prince Hal and Hotspur are played by Chris Sarandon and Christopher Walken, while Michael Allinson portrays the King. Falstaff - the backbone of any ''Henry IV'' - is essayed by a padded Roy Dotrice. Capable players, every one.

Still, the evening (or afternoon) is only a partial success. The play's energy, complexity, and brilliant verse come through much of the time. But all these qualities disappear at odd moments behind a sort of elocutionary haze, when the company cannot sustain Coe's fierce commitment to language for its own sake. During such dry spells, the production seems to obscure meaning rather than reveal it; passion dissipates into verbiage, and the play's momentum winds swiftly down.

It doesn't help that these lapses occur near the beginning of each half of the show, when moods and expectations are being established. This is especially troublesome in the first act, when Allinson's crisp enunciation seems calculated far too coolly, and even Dotrice's Falstaff seems more dull than delightful.

Other problems crop up later on. Walken's Hotspur begins as a nervous, pacing lion, but gradually diminishes to a halfhearted warrior who's only mildly interested in the peculiar death of Walter Blunt. And the finale, a lingering image of the rapidly maturing Hal, is less than electric.

Yet there are virtues aplenty in this frequently solid production. Chief among these is Dotrice, who gathers wit and wind as the scenes roll by until he's playing the audience like an instrument during Falstaff's final speeches about honor and liquid refreshment, the latter borrowed from ''Henry the IV, Part 2'' with the aim of further spicing up the later moments of the show.

Since the talented Walken is to play ''Hamlet'' in the second Stratford show of the summer, beginning Aug. 3, one hopes he finds a more sustained Shakespearean approach than he shows in ''Henry IV,'' where his early promise - a high point of the first half - just doesn't pay off later.

Also slated for the ''Hamlet'' cast are Fred Gwynne as Claudius and Anne Baxter as Gertrude.

Incidentally, the American Shakespeare Theater is still a lovely place, as rewarding in its woodsy and watery surroundings (on the banks of the Housatonic River) as in the timelessly classical material it presents. One hopes it weathers its present troubles and lives many a long year into the future. The current ''Henry IV'' is a small step in the right direction, though one wishes it could have been a larger one.