Intertherm model# FEH-015HA It is no longer blowing heat
High limit safety device is probably tripped, it should reset automatically, also check other safety's for tripped condition, they look like small round device located in a variety locations through out the unit with two wires to each one, some have small push button resets located in the burner compartment area. If all the safety's are reset and check out OK the main control board may need replaced. One of the most common causes of high limit safety device trip is lack of air flow, Dirty filters, evaporator coils, malfunctioning blowers, closed supply air registers etc.
Note: High limit safety switches also go bad after being tripped to many times.