Translate an English joke and point out the humor.

Grandpa can't keep pace with technology. One day, he called his father and complained that he couldn't use his printer. The screen says it's preheating. When my father arrived, I saw that half of the printers had melted. Father asked what happened, and grandpa said, I don't know. It's no use using a heater.

(Probably, the printer is as cold as a car. You have to turn it on to warm it up, and then Grandpa will use the heater to heat it himself. )