94 Explorer, heat and AC don't blow unless on high

Help! I have a 94 Explorer XLT and unless I crank the fan setting up to high, it doesn't seem to do much. It doesn't matter if the tempature is set to cool or heat or if the AC is on. Any ideas?

Thank you in advance!

Are you saying the blower only works on high? If that is your problem, it is probably the blower resistor.