Hi,
My 20 year old day and night model 394jaz036065 lights the pilot and after awhile fires the burners then shuts down. Now it just lights the pilot and then shuts the pilot down after a while 2+ minutes.

Is the flame sensor mounted to the ignition/pilot assembly? I am trying to confirm that- it has to be , there are no other wires going to sensors other thatn the limit switches for the vent and a second one that is mounted inside the heat exchanger area.

Does this sound like a flame sensor problem to you?? (or gas valve)

Do you have three wires coming out of the pilot and one larger red wire coming out of the spark ignitor? If this is right you may need to clean your pilot, it has to burn so big or it will not move the switch in the pilot. It is also possible that the pilot is bad and you may have to replace it. This part is fairly expensive.

Yes it has three conductors and the ignition wire. So would this be considered the flame sensor? When I try to order this part would I call it a pilot or?? Thanks for your answer.

This is not the flame sensor, you do not have a flame sensor, you have a pilot with a switch on it that has two different positions for for the sparker to spark when the furnace is calling for heat, after the pilot lights and the bimetal switch in the pilot moves to the position o turn on the gas for the furnace burners. The other wire goes to the hard pole that carries the spark when the spark goes to ground it lights the pilot.

The pilot may not be burning enough to heat the bimetal strip, therefore it never moves the switch into the right position.

Usually these are just easier to replace. It is a known problem with Bryant,Carrier,Day and Night, and many other brands from ITT.

NOTE: many people have tried to adjust these and found out they have no more safety so the furnace can and will go BANG. Replacement of the part is always best.