Blowers ramp up to full speed after upgrade of Management Module to dual or Redundant Management Module - IBM eServer BladeCenter (Type 8677)

Resolving The Problem

Source
RETAIN tip H18614
 
Symptom  
The failing mode is an event log indicating blower failure. The Blower Speed will indicate zero percent when the blowers are actually operating at 100 percent. The blowers (which are working properly) have ramped up to full speed to compensate for the "perceived" failed blower to protect the BladeCenter from overheating.
 
This failure will occur after a upgrade from a single Management Module (MM) configuration to a dual or Redundant Management Module (RMM) configuration. If the Redundant Management Module is removed, the blowers will return to the normal speed - and the fan fail light will be cleared. The RMM does not have to be active to cause this failure.
 
Affected configurations
The system is an xSeries BladeCenter, type 8677, any model.
 
The system is configured with the following option:
 
Redundant Management Module, option part number 48P7055, replacement part number (FRU) 73P9297.
   
Solution  
Replace the Redundant Management Module (RMM) with the replacement part number (FRU) 73P9326.
 
Do not remove or replace the blowers. Simply removing the RMM will correct the blower failure and return the blower speed to the correct levels.
 
Workaround  
Remove the Redundant Management Module (RMM).
 
Additional information  
The Redundant Management Module which has replacement part number (FRU) 73P9297 has a component that causes the Blower Speed readings (the tachometer) to fail. This failure will often occur immediately after upgrading the BladeCenter from a single MM to dual MM.
 
The Tachometer is reported as zero percent. Both Blowers typically are shown as "failed" at the same time in the event log. Even though the RMM is causing this failure, the Redundant Management Module does not have to be the active MM to cause this failure. Simply having the Redundant Management Module plugged into
SLOT-2 will cause this problem.
 
Removing the Redundant Management Module will correct the fan speed problem until the RMM can be replaced.