ON AN ULTIMATE IT IS USUALLY AN ELECTRONIC IGNITION.
TURN IT ON, THE FAN SHOULD RUN WHICH ACTIVATES THE PRESSURE SWITCH WHICH IN TURN STARTS THE IGNITION PROCESS.
PULL THE FRONT LOWER TRAY FORWARD AND OFF THEN LOOK FOR A LITTLE RED BUTTON, THIS IS THE O/HEAT THERMOSTAT AND MAY JUST NEED PUSHING IN TO RESET
BG MIKE
November 2006