I have a ThinkPad T60 computer here, and its fan is in one of three states, mostly the second one, which is totally annoying:

1. Running normal at slowest speed.

2. Spinning up and down between 3100 and 4200 rpm, with a cycle of 2-3 s. (Measured with psensor under Ubuntu 14.10.)

3. Running normal at full speed.

The spinning-up-and-down cycle does not correlate with any cycle in temperature sensor readings. The problem affects all operating systems though (tried Ubuntu 14.10, Windows 7). BIOS (version 2.27) and embedded controller (version 1.07) are at their newest versions. This problem is not the typical pulsing fan problem of ThinkPads about this age, because the pulsing fan issue lets the fan vary <50 rpm, not 1100 rpm like here.

The fan is an aftermarket replacement part (Toshiba Home Technology MCF-210PAM05). It is mounted into the orginal heat exchanger.

1 Answer

This problem can happen due to a hardware defect of the fan.

Exchange the fan! The Toshiba MCF-210PAM05 non-original spare part usually works fine in a T60, but seems to be broken in your case. Exchange it for a new one, or try with an old (loud but working) fan if the problem goes away.

Discussion. By default, the embedded controller will manage fan speeds. Available speed steps on a T60 are 1-7 and a "disengaged" mode for max. speed [source]. What happens here is probably this:

1. Fan is running normally at speed level 1 (~2800 rpm) while the CPU temperature reaches a threshold for increasing fan speed.

2. Embedded controller switches one speed level up to level 2 (should be ~3350 rpm), but the fan reacts badly due to its hardware defect and starts spinning at 4200 rpm.

3. Embedded controller checks fan speed in its next feedback loop, finds it too high for this temperature, switches one speed level back (to 1 again).

4. Embedded controller checks fan speed in its next feedback loop, finds it too low for this temperature, switches one speed level up (to 2 again).

And so on. Speeds are here as measured by me with a working fan, they are a bit different from those given here.

Alternative solutions. Unfortunately the T60 has no PWM controllable fan, so using fancontrol to set exact rpm speeds is not possible. One can take over fan control from the embedded controller though, but setting the speed is only possible using speed levels 1-7 and "disengaged". Of which in the case of this defect, only 1, 7 and disengaged work without the spinning up and down. And avoiding speed levels 2-6 can only be a workaround until getting a new fan; because, even when configuring it with a huge hysteresis and for hot temperatures only, the notebook will occasionally switch into the very loud fan mode 7 to cool itself down. Anyway, such configurations are possible, using TPFanControl under Windows or thinkfan under Linux.

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