Laptop fan running at high speed

Hardware Hub Laptops & Netbooks
1

So two or three weeks ago I shorted out my laptop motherboard while changing the heatsink. It was my own dumb mistake. I was trying out a different version of the heatsink, as my laptop (a ThinkPad T420s) has two different fan styles. I was trying to find out if the other kind was quieter. But one of the wifi cable connectors came in contact with the motherboard somewhere when I was removing the palm bezel. I had forgotten to unplug the AC adapter. Now that motherboard can't tell when the AC power adapter is plugged in.

So I bought two new motherboards (different processors, as they are soldered to the board). And a handful of different heatsinks. What it boils down to is this: on both new motherboards, with three or four different styles of fans/heatsinks (3-wire and 4-wire), whatever I try the fan ramps up to max RPM after a minute or so. It never backs off, just sits there at 4k RPM. All temps are normal, nothing looks out of place or wrong. The fan just ramps up, and the only way to reset it is a complete shutdown.

I have tried both motherboards, different fans, new thermal paste, different screens/lids, different memory, different palm bezels, with/without batteries, with/without AC adapter, flashing the BIOS/UEFI. It does it in Fedora and Windows 7.

I just can't figure out why the fan ramps up to full speed like this. There has to be a reason, and I can't see it. I have been using my MacBook Pro for the last two weeks, and I am about done with it. I can't stand using it anymore.

Anyone have an idea of what could be going on?

2

Does the fan report the proper speed in a fan monitoring program like Speed fan? So laptops will set the fan to 100% if no speed is reported.

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Yeah, all the monitoring programs I have checked report the fan speed. From cold boot the fan seems to act fairly normal, cycling up and down based off system load. If windows gets done loading in time it actually spins down like normal. Soon thereafter it ramps up to 4000 RPM and stays there.

4

Sounds like the laptop is running hot ... or at least thinks it is.
Run Speccy portable as soon as the PC has booted and keep an eye on the temperature. Either a sensor has gone wonky or something is wrong with the cooling itself.

Also feel the exhaust. Is there lots of lukewarm air coming from the vents or is it a small amount of hot air instead? In the latter case, there is something clogging up the cooling fins.

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I take that back. The only program that sees the fan RPM is HWiNFO in windows and sensors in Fedora. Both SpeedFan and OpenHardwareMonitor do not see RPM. Not sure what that means.

I am almost positive that airflow is not a problem. The air blowing out is cool to lukewarm. Temps reported are very reasonable. It's possible that for some reason the fan speed isn't being sensed properly by the BIOS. I am going to swap the motherboard for another one and a different heatsink to test.

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6

Same exact thing. Different motherboard, different heatsink (same model as previous one).

Trying to figure out what components are the same between the swap. There's a small power board, but that's a new one, not the one from the system I shorted. There's a small board that the SSD plugs into, which then plugs into the motherboard. Not sure if that's from the original system or not. The two SSDs I am using (one windows 7, one Fedora) shouldn't be a problem. The two batteries are from the original system, but it does the full speed fan with or without the batteries installed.

Edit:
Decided to put the original, shorted out system back together to test. It does the same high speed fan thing, with a completely different style heatsink (this board has dedicated graphics and an i7). The only things that transferred from the other system(s) were the batteries, the WiFi card, the RAM, the SSD, and the AC power supply.

I started by using different battery, replacing the secondary battery with a DVD drive. No change.

Replaced the WiFi card with one that came from one of the systems I got off ebay. This seemed to make a difference, but it went right back to the max speed. Don't know what to make of that.

Replaced the memory. No change.

Can't replace the AC power adapter, don't have another one. Seeing as it does the fan thing running on battery I don't think the power adapter is the problem. Tried cold booting without the power plugged in. No change.

So that basically leaves the two SSDs I have been using. I can't see that they'd physically be damaged, but I think I have a brand new spare mechanical hard drive I can use to test that out. Maybe it's driver related, even though all known drivers are installed in Windows 7. Maybe I will try this tomorrow night after work.

edit edit:
Just noticed Windows 7 turn the screen off after its set time. Immediately as the screen shut off the fan quickly ramped down. I let it sit for a minute or two, and the computer didn't go to sleep, and the fan stayed off. I moved the mouse and the screen came back on, the fan RPM at 0. I started Firefox and the fan came on its lowest setting, then ramped up to 4k and stuck there.

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This laptop have a dedicated GPU? i could be a bad bond between the GPU and heatsink.

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The two motherboards I bought as replacements do not have dedicated graphics. The original board I shorted does.

I am going to be doing fresh installs of both windows 7 and fedora on a new hard drive tomorrow to rule out driver issues.

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So far it isn't looking good. I used a brand new 1TB mechanical hard drive to install Windows 7. During the install the fan seemed to behave normally; it would cycle up and down, but it never seemed to get stuck at max. After the first real boot into Windows it seemed alright for a while (several minutes). Before I even started installing drivers the fan ramped up. I installed all the drivers anyway.

So I thought, alright, I know I don't have the screws in the motherboard. Maybe it needs a ground or something. So I put them all in, and mostly secured the palm bezel too. Didn't help.

If I boot into windows and just let it sit there without doing anything at all the fan stays at minimum RPM. After a couple minutes the fan ramps up to 4000 RPM for no apparent reason, and it stays there until a full shutdown.

Fresh install of Fedora does the same thing.

Two different motherboards, and two different fan/heatsinks do the same thing. Minimal, if any parts are used between the systems.

Why?

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That makes me think there really is a temperature issue. Perhaps some part of the laptop is now missing a thermal pad and the sensors are picking up that the part is overheating?
At this point I'm guessing, but this makes more sense than anything else I can come up with.

The only suggestion I can make is to run hardware monitor as soon as it boots and keep an eye on all the temperatures to see if one is rising.

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11

You know, that is exactly what I figured too. It acts like something is hot. HWiNFO is a pretty in depth monitor, it shows a lot of information. All the temp sensors it displays look perfectly fine. No part of the laptop physically feels warm apart from the RAM and WiFi module. I can actually touch the heatsink directly above the CPU and it is cool. There is a chip with a thermal pad that makes contact with the keyboard when it is installed. Every time I put the laptop back together I make sure that pad is in place and the keyboard is screwed down to ensure that chip is dissipating its heat.

So I am not sure. I will look over one of the other boards I have to see if I can spot anything I am missing. In any case, what I think I will do is disassemble both laptops I have now and lay all the parts out. Just to see what's what. I labeled most of the original parts from shorted system, just on the off chance any of them got damaged.

Probably won't be doing that tonight, though. Not enough time. I am getting to the end of my rope with this. I have been fighting for the last couple weeks, ordering parts I don't need, not making any progress, dissembling and reassembling the same laptop over and over. The Dell Latitude E7440 I have been eyeing is looking pretty tempting right now. I just don't want to drop $300 to $400 on a laptop when I have enough parts to make two.

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So today I completely disassembled everything I had put together and looked everything over. After determining which parts went to which system (original shorted system, ebay system) I put together the two systems from the ground up. I completely put the systems together, all the way through to the last screw. And, to my surprise, they both work as they should. The fan in both systems act completely normal. I have no idea what the difference is, or why it would make a difference that the laptop is screwed together.

I guess it's possible that something on the motherboard needed to be tightly in contact with either the base of the laptop or the palm bezel, as both are metal (magnesium), to dissipate heat. Maybe a component temperature is monitored that isn't passed through to the OS. Not sure.

In any event, I bought a new laptop on Thursday. I got a Dell Latitude E7440 for a really good deal. Should be getting it this coming week. I feel like it will be better quality (physically) than these Lenovo T420s laptops, which are brittle.

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