1998 Chevy Malibu Fan relay

You have a Blower Motor Resistor that controls the speeds of the motor. If the motor runs in high, but doesnt in one or more of the lower speeds, suspect that resistor as your problem.
To replace it you must remove the blower motor, and it is in the ducting behind the motor. It is bolted to the outside of the ducting, with the resistors in the air stream. You may have to cut the dash mat a little bit to gain access to the back screw.