He’s really in hot water.

A “rent a vet” hot dog vendor was arrested yesterday in front of the Metropolitan Museum of Art after he locked himself in his car and refused to accept a summons for illegally doing business, police said.

Armando Crescenzi was busted at 3:30 p.m. and police briefly confiscated his food cart.

He was charged with obstruction of government administration, police said.

Crescenzi claims the legal right to sell under a decades-old law that allows disabled vets to hawk merchandise on city streets without paying for a permit.

That has set off a battle with other vendors, who pay tens of thousands of dollars for city permits.

They claim that their business is being stolen by the “black-market” food- cart owners who circumvent the law by hiring disabled vets.