What a dud!

A Yonkers man thought he found an active landmine in his grandfather’s attic yesterday — and instead of calling cops, he caused chaos by walking the thing over to a nearby firehouse.

His dopey move shut down Fire Station 13 and forced cops to cordon off a busy business area for nearly an hour and a half.

Officials did not release the name of the man, who appeared at the firehouse at about 1:25 p.m. with the suspected explosive in a box.

People who find a suspected bomb are not supposed to touch the device, said Yonkers Police Lt. Pat McCormack.