I have an 1998 Accord and the fan switch ran on only one speed. I
thought the switch had broken. I was dreading having a dealer or
mechanic pull the dash apart to rplace the switch.

It turns out the the plastic on the fan speed knob (female connection)
had cracked. I pulled the knob off (pull towards you)and replaced it
(slide a new knob on) and the fan was fine. I have all 4 fan speeds.

This does not explain your heat or AC? ??