Thanks for writing. It's a little tough to say for sure why your wisteria isn't blooming well if it's in full sun.
Do you know if it was grown from seed? Seed-grown plants can take a number of years --- more than 10 sometimes, before they start to bloom for the first time. So if it came from a seed (vs. a cutting), then patience may be the best bet.
Do you prune your wisteria? Pruning at the wrong time of year can keep the plant from blooming profusely. (The best way to prune is, in winter, to cut the main leader shoots back to just five buds or so leaf buds.)
Do you fertilize your wisteria? Too much nitrogen fertilizer can spur the plant to put on lots of leafy growth at the expense of blooms. Keep in mind that if you fertilize your lawn and the wisteria is near your lawn, that it may be absorbing nitrogen from that.
---Justin, Senior Garden Editor, BHG.com