I have a nordyne heater/ac unit. We woke up in the middle of the night last night and heard the heater unit fan running but the blower never kicked on. We tried switchin it to air and it started blowing right away. What could be wrong? The ignitor? Also my fiancé looked the light and it said it blinked twice? Any Ideas?

Find the service legend that describes the observed activity of the LED - should be inside one of the access panels, or on the control board itself.

We saw the legend and it says pressure switch is open. So what does that mean?

Several possibilities... clogged/restricted flue, clogged/restricted drain tubes/trap (if this is a condensing furnace), clogged/restricted pressure switch tubing/ports, faulty pressure switch.