Thank you for your list of possible causes. No fuse. I go to the circuit box with red and black under dash. I suspect that your hypothesis about voltage is correct. My read out indicates low voltage. I put the battery on the charger to bring it up to full charge. Only two years old. Hope this is not persisted problem. Connections on back of unit are tight.
Could two batteries series together provide more voltage and solve this problem or would create a new problem?
Joe