T60p/T61 Frankenpad fan not spinning when hot

[bloovis]

I've been using my Frankenpad (T60p with T61 motherboard) for several years now with great success, running both Linux Mint 18 and 20. Just this week I noticed the machine was smelling hot, and I realized the fan was no longer spinning at all. Usually the fan runs pretty much all the time, even when the CPU usage is low. I'm not running any kind of fan control daemons in Linux.

Investigating some more, I saw that the fan did spin up for a second at power-on, but never after that. I then tried experimenting with manually turning on the fan, as described in this thread on stackexchange: https://unix.stackexchange.com/question ... art-needed. I didn't use thinkfan, just wrote different level values to /proc/acpi/ibm/fan, as described in the first answer on that thread. Writing numeric levels like 1 or 5 worked fine: the fan came on and stayed on. But writing 'auto' to the level turned off the fan, and it never came on again.

So my question is: how does the BIOS know when to turn on the fan automatically? I'm assuming it uses a temperature sensor to decide. The ACPI CPU temperature sensor seems to be working OK, and I can see the temperature rising steadily in Linux as the machine warms up. Does the BIOS use some other sensor, and could that sensor somehow be failing? How can I debug this problem?

[m11k]

I have noticed that the fan in my T61 frankenpad does seem to be a bit less responsive than on my T430. I think it just doesn't seem to have a "low speed" settings. It pretty consistently turns on when the CPU temp is above 65, and turns back off when the CPU temp is below 60. I don't know if the fan speed is controlled by Linux, or completely in the BIOS. I do have TLP installed, but I don't recall modifying any of the fan settings. I'm running Debian 10 w/ kernel 4.19. I don't think it matters, but I also have the middleton BIOS installed (as you probably do as well).

Maybe try clearing the BIOS settings, and unplug the CMOS battery to really reset everything?

[axur-delmeria]

Since you're using Linux, you can install Thinkfan and set the fan thresholds manually.

[bloovis]

Thanks for the replies. It may have been a false alarm. I put fresh thermal paste on the CPU and GPU, and disconnected/reconnected the BIOS battery. Probably none of that made any difference. Eventually the fan came on when the CPU got to around 70 degrees C, and has stayed on ever since, even after the temperature dropped to 47. This was probably the normal behavior, but I've got enough ThinkPads here that I must have forgotten about this one.