My Rheem Furnace will ignite the flame properly the blower will start but shortly after the flame will go out before heating properly. Could the flame sensor need replacing or should or replace the thermostat control?

My Rheem Furnace will ignite the flame properly the blower will start but shortly after the flame will go out before heating properly. Could the flame sensor need replacing or should I replace the thermostat control?

Try this cheap trick first. Clean the flame sensor with steel wool or fine sand paper (do a good job). It might not be the fix but it is free. If that does not work post back.

Where is the flame sensor on a Rheem Criterion (NOT THE CRITERION 2). Thank you for any help you can give me.