Rheem furnace burner problem?

[parkerbrother]

I'm haveing a problem with my Rheem furnace(model # RGDG-050AUER)blowing cold air. Sometimes it blows warm air then cold again. The pilot light is lit and the fan blows but the burner doesn't ignite all the time. Any help/suggestions would be greatly appreciated.

[parkerbrother]

Any suggestions on what to look at first? Anyone?

[Joel]

It could be the flame rod is dirty it is a rod you will find on the last burner and is easily removed with 2 screws sand it with fine sandpaper and replace it this should take care of it (it may need replacing)