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October 26th, 2014 00:00

Precision T3500 CPU Fan always on full speed


I have a Precision T3500 which, when turned on the CPU fan spins at full speed constantly creating a lot of noise. This has only happened recently, despite no changes to software, hardware or environment.

Things I have checked and tested:

- There are 2 fans, one for memory, one for CPU. It is only the CPU fan spinning too fast.

- I swapped the memory fan and the CPU fan but the same thing happened so it is not an issue with the actual fan.

- I checked temperatures and they are all in normal ranges

- I read about some cases having a switch on the side panel which is turned on when the case is opened. This case does not have that.

- The BIOS etc.. is all up to date with latest version available on Dell support pages

- I've tried downloading some software to control fan speed but no software is able to read the fan speeds or control them. I think this is just a limitation of this particular model.

Does anyone have an idea what the problem could be? Are there other things I can test for?



10 Elder


43.2K Posts

October 26th, 2014 16:00

If you reboot and press F12, do you have the option to run hardware diagnostics (might be on Utilities partition on F12 menu). If you have them, run the fan diagnostics to see if the motherboard is correctly seeing the fan.

Have you checked to make sure the heatsink is properly locked in place on top of the CPU?

Might be dried out thermal paste. You'd have to remove the heatsink, clean both surfaces and apply a thin coat of fresh thermal paste, eg Arctic Silver, before reinstalling the heatsink. Check the manual for instructions to remove the heatsink...

4 Posts

October 26th, 2014 21:00

Thanks for the reply Ron

I tried the diagnostics and it all went through fine.

I checked the heatsink and it's locked in nicely too. I can try applying some new thermal paste, but if the CPU temperatures are fine then I'm confused how this could help?

Thanks again


4 Posts

October 27th, 2014 04:00

Update to my problem. I installed speedfan which listed the 3 fans in my PC. GPU fan, and 2 case/CPU fans, it listed the fan speeds and showed my problem fan as fan number 1 with its high speed. I could control the speed of the gpu and memory fan, but this CPU fan would not budge. I then thought maybe I could run both fans off the memory fan socket and control the speed manually but it looks like the dell motherboard has some rare 5 pin, 4 wire fan cables so my ability to buy an off the shelf cable splitter might not be possible. Any other solutions you can think of? Thanks Simon

10 Elder


43.2K Posts

October 27th, 2014 14:00

Did the CPU fan pass both low and high speed tests when you ran the diagnostics?

Dell CPU fans have a sensor in them that BIOS needs to see. That's why SpeedFan can't control them. (I've used SpeedFan for years to monitor temps in this Dell.) And if you connect a non-Dell CPU fan, you'll get a "Fan Failure" error at every reboot.

The CPU temp may be ok only because that fan is running at top speed. If the thermal paste dried out, the fan may be compensating by blasting.  But no guarantees new thermal paste will solve the problem... :emotion-5:

4 Posts

October 27th, 2014 18:00

Hi Ron

Yes, the diagnostics completed and a pass for everything. The front panel diagnostic lights are all fine too on boot, post etc...

I did manage to use speedfan to control the GPU fan and the memory fan. I had to turn on the 'Dell' option in the options window.

I will try the thermal paste but not convinced - the CPU fan goes to full speed the second you turn on the PC. It feels like there's some sensor gate stuck open.

Thanks for your time Ron.


10 Elder


43.2K Posts

October 27th, 2014 20:00

Before you redo the thermal paste, you might want to completely uninstall the video driver, reboot and then install the latest video driver for your hardware and version of Windows.

Some times a corrupted video driver can cause the fan to go crazy.

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