# What's special about Compaq case fans?



## wlb628 (Mar 4, 2008)

I'm trying to replace the noisy 92mm case fan in a Compaq ProLiant M330 server with a quieter fan, but there's seems to be something "special" about the original fan (it's a Nidec TA350, model M34789) that the BIOS detects on startup. The original fan is incredibly noisy, even at its lowest speed, and the machine doesn't get hot because it's not really being used as a server any more -- just as a standard desktop machine.

The fan I've tried to substitute is an Antec 12 volt, 3 wire fan. The new fan has red and black power wires and a yellow tach wire, which I soldered to the same color wires in the original fan's wiring harness and plugged into the original plug on the motherboard. The new fan seems to runs fine. Its speed is varied by the motherboard, just like the original was (it goes full speed for a couple of seconds at power-up then slows down). But I get an error message during bootup that the system fan is missing or has failed and that the machine will shutdown in 5 seconds. There's also an LED on the motherboard that lights, indicating a system fan failure, according to a sticker on the inside of the case.

Can anyone tell me what it is that won't allow the system to detect a fan other than the original one? The only thing I can see in the specs of the original fan is that it draws a bunch of current -- 1000 mA or 1 amp -- most fans draw only a few hundred mA. Although it seems like a counterproductive solution, I could add a dummy load (resistor) across the fan's power leads to draw more power.

Any advice will be appreciated.


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## V0lt (Sep 14, 2002)

The solution might be simpler... have you checked through the BIOS settings to see if you can disable automatic shutoff on fan failure?


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## wlb628 (Mar 4, 2008)

No, I have not tried disabling the system shut down in the BIOS, but I will certainly check that out. That would be a wonderfully simple solution, indeed. 

As it stands now, the machine has to get farther into the boot process for me to be able to get into the BIOS -- it stops on the bad fan warning upstream of the BIOS entry point. So I have to get another similar machine (the company has 4 of them) to avoid having to reconnect the old fan to the wiring harness on this one.

I'll post a follow-up after I've taken a look at the BIOS. Thanks for the suggestion.


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