blower stays on high, even when ignition switch is off

I have a 96 ford explorer Ltd and the heater/blower motor stays on full blast, i have to take the fuze out to stop it. This happerns even when the engine is off and no keys are in the ignition. Could anyone help me with this problem.

replace the blower resistor first

not for sure, but there is probably a set or relays for the higher current appliances. if the relay is stuck closed, it would run constantly. the key probalby pulls in the relay signal side, the orthe side is direct to the battery (as is the fuse).