Amana sise-by-side quit working--possible short in heater wiring

[Walter C]

I have a 1991 Amana sise-by-side working perfectly all these years. 2-3 days ago I noticed lights in house flickering--not sure if connected to problem.
Today the fridge stopped working with all lights on and can feel heat in inner rubber door seals.
I see a black smudge on upper corner edge of freezer door--upper corner that's adjacent to other door where they meet at midpoint of frame.
Can see continuation of black smudge into seam of door jamb where blackened area would meet the frame when door closed
Smudge is size of thumnail and does not wipe of easily.
What would i check to see if some kind of shot has occured--or other troubleshooting checkpoints to see why machine dead in the water?
Is some kind of short inheater wire that warms around door gaskets possible?

[Walter C]

Found problem. Defroster timer quit. Replaced for $38 from RepairClinic.com. Thanks for the help.