Last week my air handler quit working, I found that the 5AMP fuse for the secondary 24volt pwr supply was blown, replace and all worked fine for a week. Now I find it blown again, but each time I relace it it blows, The voltage reading I get at the fuse is 29.5 V is that to high? The transformer is 60hz/208v/230v 24 V load 40VA. Or may it be the 24V circuit board?