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can you monitor fan rpm while using rheostat????

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Senior Member
Dec 18, 2000
Germany->Bavaria-> Augsburg
Hi guys and gals,

I just wondered if it would be possible to monitor the fan rpm with MBM5 or HWDoctor while using a rheostat. I did the 7V mod to my Delta Black Label and the software and also the bios can't show me any fan rpm. It's always 0 rpm. I know that it's possible to monitor the fan rpm at lower voltages than 12V and that's the reason why I thought that it could be possible with a rheostat.

Please post your experiences or opinions!
If the fan has the third white wire for monitoring you could hook that wire up to a separate 3 pin connecter. Then plug that connecter into the fan header on the board. You should be able to monitor it then. Just make sure the wire makes contact with the right pin on the board. I believe it's the far right. But you may want to double check.
Yes, you can. Just don't put the rheostat in the black (minus) wire. The tachometer output uses that as its return path. In the 7V mod, that is why you can not use the tachometer output. The minus wire of the fan does not go to the minus wire of the PSU. That is yet another reason why the 7V trick is not good electronics practice.