The gas fires for a few seconds and then shuts off and restarts the cycle again. Usually it works the second time. Sometimes it locks out and has to be reset. I've cleaned/replaced the flame sensor. I checked the vacuum switch -ok

Do you have an led light that flashes a code for you to interpret. I am sure that you have made sure that the filter is clean. If you can give more info on how it act at the first light up it would help.

Test flame sensor.

Do you have an led light that flashes a code for you to interpet. I am sure that you have made sure that the filter is clean. If you can give more info on how it act at the first light up it would help.

I don't know if the led flashes a code. It might even just turn on -not flash at all.

At first light up, it acts normal for a second or two, then shuts off the gas and acts like it's starting over again -flew fan runs, igniter starts to glow, and about a minute later, the gas starts.

Check air press. Switch for quick open and close occurrences

I had a similar problem where my Amana AMV9 would cycle on and off. The ignition would lite the flame and stay lit for a few seconds, but then go out. I cleaned the sensor with fine sand paper and it seems to be working fine. It was cycling on and off with NO blinking codes resulting. I plan to also purchase a new sensor to replace this one. Hope that helps!