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Entry type: FAQ Entry ID: 14493622, Entry date: 03/03/2003

Defective SOM/SOL message regarding processor fan in SIMATIC BOX 840, Rack 840 and Panel PC 870

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The SOM/SOL monitoring software issues an alarm for defective processor fan or shows a fluctuating fan speed of 0 to 4000 revolutions although the fan is visibly running at a constant speed and shows now sign of being defective. What could be the reasons for this and how can this behavior be remedied?

In the Rack PC 840 and Box PC 840 and Panel PC 870 devices it might happen very rarely and sporadically that at very low fan speeds the speed value cannot be captured properly. 

This can be recognized by the following symptoms: 

  1. The display of the processor fan speed in the SOM/SOL application fluctuates very strongly (0 to 4000 revolutions).
  2. A fan alarm is displayed by the SOM/SOL application.
  3. The red FAN LED lights on the front of Rack PC 840. 

The processor cooling system is not affected by a defective display.

Replace the SOM.SYS driver file with a version lower than V2.0.4.2 with version V2.0.4.2 or higher.

Version check:
The "SOM.SYS" driver is in the following system folders depending on the operating system being used:

  • For Windows Millennium and Windows XP in "C:\Windows\System32\Drivers
  • For Windows NT and Windows 2000 in "C:\Winnt\System32\Drivers
  • The file version for "SOM.SYS" is displayed by right-clicking the "SOM.SYS" file.
  • Now select the "Properties" field and switch to the "Version" tab. 
  • You can tell that installation has been successful by the fact that the appropriate SOM.SYS driver is running on the operating system concerned.

Operating system

Driver version

Windows Millennium

WDM driver V2.0.4.2, Build 001 of 15.01.2003

Windows NT

Kernel driver V2.0.4.2, Build 001 of 15.01.2003

Windows 2000

Kernel driver V2.0.4.2, Build 001 of 15.01.2003

Windows XP

Kernel driver V2.0.4.2, Build 001 of 15.01.2003

Table1: Versions of the SOM.SYS drivers

Driver download and installation instructions:

som-disc_v2042.exe ( 735 KB )  

The installation instructions "Install.TXT" are in the EXE file.

Version update, SOM, Safecard On Motherboard, SOL, Safecard On LAN

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