As mentioned above test the element.
Remove one side of the wiring to the element. Now with the AC on test across the wires coming to the element for 110 volts. If that is Good. disconnect the AC and with an ohm meter test the wires going into the element. If you do not get a reading there the element is open. If you did not get 110 when testing for it the board may be bad or power may not be getting to the board. Test the input to the board for 110.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles