Miller CMF 80 PG CONV gasfired heater won't ignite. I turn up the thermostat to activate the unit and the bottom motor runs for about 30 to 45 seconds. Then it sounds like it has ignition for 2 seconds. Then it goes back to the fan motor running for about 30 seconds and appearing to have ignition for another 2 seconds. It repeats 2 more times and then gives me a 3 blink code. The code keeps blinking and unit won't attempt to start again until power is cut or the thermostat cuts power. There is no sensor. I have replaced the ignitor. This is the third time for the ignitor (this time it wasn't bad). Does any one know what the problem is?