Thank you for your suggestion. For the sake of thoroughness, I will attempt to replace the small module 6 fuse; however, I am skeptical that it is the source of the issue, as we utilized the heated seats without incident last winter. I first identified this problem last summer while the third row was occupied during a trip with my grandchildren. I am uncertain about the duration of this malfunction, since I have hardly used the third-row air conditioning since purchasing the vehicle new. I am uncertain if the back control knob illuminates at night when the headlights are on, or if it ever did so. Uncertain about what the illumination from the headlights will indicate, assuming it provides any information at all. I now believe I need to inspect the wiring connections for the dashboard rear AC button and the third-row control/switch to confirm their security; however, I imagine they are snap-together plugs that are typically rather secure. Inspecting the connections visually is likely to be a cumbersome task, particularly for me to reach the connection at the rear control, since the only access panel nearby does not expose the wiring for it.