The general manager shall hold office for an indefinite term and may be removed by the board only upon the adoption of a resolution by the affirmative vote of not less than three members of the board of a five-ward district, or four members of the board of a seven-ward district. Before the general manager may be removed, he shall, if he demands it, be given a written statement of the reasons alleged for his removal and he shall have the right to be publicly heard thereon at ta meeting of the board prior to the final vote on the resolution providing for his removal, but pending and during such hearing the board may suspend him from office. The board may not reduce the salary of the general manager below the amount fixed at the time of his original appointment except upon the adoption of a resolution by a like vote and after a like opportunity to be heard. The action of the board in suspending or removing the general manager or reducing his salary, if approved by a majority of the membership of the board, is final.