Have you considered this?
To make a 12vdc fan work, the kind that is found in a computer, you have to convert 110vac - the power that is found in the wall - to 12vdc.
What your dad did was add a 110vac/12vdc converter so you could plug it in. I've done it plenty of times.
If I was to guess, I'd say somewhere in his wiring, something has come undone.
Put the stickers back on, put the oil away and check that wiring.