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New Member
Mar 16, 2017
Hello, I have a hp h9 1170t desktop pc. I am trying to control it's fan speeds using speedfan. When I open speedfan, there are 4 fans listed, but 2 are listed at 0 RPM. The other two are a CPU fan and a chipset fan. There are 3 PWM values (Pwm1, Pwm2, Pwm3). There is one ISA temperature sensor listed, "F71858", that is associated with all "4" fans in the "Fans" tab.

I can't get speedfan to auto-adjust fan speeds based on temps, despite reading many tutorials, and at the moment, I am trying to understand/figure out what PWM1, PWM2, and PWM3 correspond to. How can I figure this out? Thanks!


New Member
Mar 16, 2017
Thanks! I think that only the CPU fan is PWM. The VRM fan has 3 wires. Those are the two fans that show >0 RPM in Speedfan. If the other two fans reported are valid (obviously, they are not actually running at 0 RPM), I'm guessing they are the GPU and PSU fans. So, if there is only 1 PWM fan, why would I have 3 separate adjustable PWM settings? Most importantly, what does each one control? Varying them one at a time is not providing me with any diagnostic information...


Senior Member
Dec 27, 2008
I don't have any answers for you but I can tell you I have always been frustrated with Speedfan as a fan speed controller, which is it's main purpose for existence. Haven't used it in years but back then to be able to control fans the motherboard's chipset needed to be in Speedfan's database so that left a lot of motherboards unable to work with it as a fan speed controller.

Have you looked into drive bay fan speed controllers? That would do what you need to do if you have an external unoccupied drive bay. They come in both 5.25" and 3.5" sizes for full width or narrow drive bays. Here are examples:




May 4, 2011
I recommend this controller personally:


6 channels*6 individual fan controls*

30 watts per channel, this means you can use a splitter and use up to three fans per channel, or very high powered fans without issue, ie Deltas. very durable, and sleek looking.

numbers light up blue, green, red, white and orange. led switches with a small button.
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