I have a 2000 Chev Impala LS 3.8L. After changing the fuse for the fan
heater one morning, the fan now only works on maximun speed. Is there a
relay of some sort that I need to change or is it only the switch that is
defective. All suggestions or comments would help.

Thanks

Your fuse probably blew because the resistor went bad. Call the
dealership, have your V.I.N. handy and tell them you need a "blower motor
resistor". They are usually located under the hood near the firewall on
the heater box or behind the glove compartment on the heater box and cost
about $20.

JL