Zippy M1S2-5500V4H - Manual (Page 9)

7) Tighten the screws of the power module.
8) If you want to test this new power module and simulate the defective situation,
please refer to Section 1.7 Installation & Testing.
Remarks: If the DC fan of the power module fails, you have to replace the power
module. Please follow the Hot-Swap Procedures for replacement.