When power is turned on and thermostat is on auto blower runs all the time ar18-1 Goodman

Disconnect all thermostat wires from the furnace itself. Still run? (make sure to kill power to the furnace before doing this, then turn it back on.) Are you getting any heat at all? Could be a tripped limit, bad thermostat, bad control board, bad stat wire, etc. One step at a time.