Drain pump is normally used on PAC unit to pump out water and jelly residue from the water tray of the ceiling cassette to be dispelled out through the drainage pipe. Without regular maintenance of the drain pump, this will cause the drain pump to be choke with the jelly residue and causes the motor of the drain pump to overworked and overheated. With regular maintenance, we can ensure that the drain pump is always at its optimum condition. Thus prevents E9 error code from happening.