I have a 2000 Cav.

Speeds 1 and 2 on the fan don't work, but 3 and 4 do.

Suggestions?

Probably the blower motor resistor. It is in the engine compartment on the a/c blower box setting next to where the fan is. Normally though you would lose the high speed, when the resistor goes bad.

was just checking the service manual for your car. with the condition you describe it is saying to replace the blower motor switch. Though it does not appear to be serviceable, so you may have to just replace the ac control head. Good luck