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Laptop fans spin during boot, don't spin at all after boot even during high temps, causing overheat shutdown


Jul 3, 2011
Hi guys, would really need some help here as I'm basically experience a laptop problem and attempting to fix it while I'm on holidays (frequent usage basically).

So pretty much as the title says, I've had the problem ever since I've disassembled and reassembled the laptop. It was an attempt to dust out the laptop before I took it with me on vacation since the fans were clogged with dust and I wanted to thoroughly clean it. At the same time, I ended up cleaning and reapplying the thermal paste on the CPU and the GPU heatsinks since I had already gotten that far in disassembling the laptop.

Now after reassembly, I'm left with a laptop that boots up and does not have any sort of cooling control after booting. When I'm in the BIOS screen and on boot, the laptop fans run. Otherwise, they do not run at all but the computer boots to Windows normally. Using CAM, the PC does not detect the fans even though they spin on startup.

Because the fans don't spin, any attempt to do heavy work on the laptop will send the temps to 80+ with no fan and then eventually result in shutting down the laptop to prevent overheat damage.

I'm at a loss here, I tried readjusting RAM sticks and unplugging and replugging fan headers so far.

CMOS Battery maybe? I did try to remove it while disassembling the laptop but then realized I didn't need to so I ended up removing it halfway and then pushing it back in.

For reference, I used ArcticClean products for all stages of reapplying thermal paste.


If you partially removed the CMOS battery, you may have cleared the BIOS settings. It might be necessary to go into the bios and see if there are any user configurable settings for the fans. On laptops, there usually aren't but there may be a setting for active versus passive fan operation.

It's more likely that you may have either missed reconnecting the fan plug correctly by one pin to either side (Doubtful since those generally sit IN a socket, rather than just having an open pin arrangement like on desktop fan connections) or bent a pin in the fan header socket when connecting it. Either that, or one of the very delicate fan wires was pulled just enough to break the connection for the speed control circuit. Really, if the fan works as you say it does but does not work after booting into windows, you might also want to check the advanced power configuration settings in control panel.

Open the power options applet in control panel, (Type control in any search or run command box, hit enter) click on change plan settings next to your current power plan, click on change advanced settings, open processor power management and make sure that the cooling policy is set to active rather than passive.

If that is not the problem then you may need to simply replace the fan as it's likely one of the wires was damaged on the speed sense circuit. It doesn't take much pressure on those very delicate, fragile wires to break the internal connection.
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