Mine on a '92 seems fine.
In the '92 FSM on page AC-32 it talks about a Fan Speed Control Resistor, but that's probably for the AC fan.
But page AC-36 shows the "Front heater Blower Resistor". It looks like it is a wire wound resistor, with different contact points for different speeds. If the end of the resistor is fused to skip some of that resistance, that would speed up all fan speeds.