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Fixing the thinkpad T43p fan noise problem

The T43p has a real problem with fan noise. It uses a brush-less fan made by Toshiba. A very similar fan is as well used in later models such as the t60, t61 however in those computers the fan makes only a noise when it is not properly greased. In the T43p it makes almost always a rrrrrrh sound. I am not exactly sure why the t60 is better than the t43. It might be related to the driver circuit. The fan design in the t60 is also slightly different. In any case the T43p produces excessive fan noise. It emits a rrrrrrh sound when the speed is controlled by a PWM speed controller.

IBM is in the process of outsourcing its laptop devision to Lenovo. This causes management bloat and loss of technical competence. You need more managers to run the outsourcing project and coordinate everything with Lenovo. At the same time you loose all your competent people because they might not want to go to China. This results in a very obvious manufacturing defect with fan noise that any t43 user will notice immediatly. A healthy organization would have investigated the thinkpad t43 fan noise problem but IBM just ignored it.

The Toshiba brushless fan

The Toshiba fan is a brush-less fan and the bearings together with the electronics and motor coils are mounted on the aluminum case. The fan rotor has inside the cap some permanent magnets. The motor coils generate together with the electronics a rotating magnetic field and this causes the magnets in the rotor cap to follow the field. The fan turns.

A fan similar to the t43 Toshiba fan. You can see how it works however this is a thinkpad t60 fan. The t60 fan is similar in design from the outside but the end of the bearing hole (can not be seen here) is different. The size of the the magnet inside the rotor is as well different but this picture is just to give you a basic idea as to how this fan works.

The rotor has a simple straight axle which just slides into the bearing. The magnets hold it at the right hight. If you would open the fan case then you could just pull out the rotor.

The thinkpad fan noise problem

There is no hole under the sticker of the fan. The axle of the fan will hover in the magnetic field but a pulsed electric current from the PWM contoller will disturb this field and cause the fan to vibrate a bit up and down. The axle will hit the aluminum case and this causes the annoying rrrrrh sound.

Here is a sound sample. Note that it will not always sound exactly the same. For some reason there are days when it's worse or better.

Another problem with this missing hole is that you can not lubricate the fan unless you take it totally apart. It is not possible to take it apart in the thinkpad t43p since the aluminum fan housing is bonded to the copper heatsink. This is another design flaw but IBM fixed that in later models. There is still no hole but the fan case is not anymore permanently bonded to the heat sink.

A solution for the fan noise problem: drill a hole into the case of the fan

The solution is to drill a 2mm or 2.5mm hole through the sticker and the aluminum such that the axle has more room to move up and down. A 2mm drill is enough if you manage to hit exactly the center. 2.5mm is better in case you end up slightly off center. The axle of the rotor has a diameter of 1.5mm. The problem is you can not disconnect the fan from it's case. You have to drill the hole with the rotor and the fan electronics in place. In other words you must drill it at the right place and you must not fall through with your drill otherwise you will damage the electronics and the fan bearing.

It is however possible to do this since there is a bit of space and the axle will move away a bit when you hit it with the drill. Never the less be careful when drilling and do not push too hard. Use a sharp drill and low speed.

Note: It should be all aluminum under the sticker. If you find plastic then don't drill because you can not fix that fan in the same way.

Heatsink and fan unit. You need to drill a hole through the aluminum plate below the sticker.

I suggest to start by carefully marking the center and measure multiple times. Use first a drill smaller than 2mm and then inspect the small hole to see if you are in the center or not. When you continue with the 2mm drill then you can still correct your position slightly. I put a plastic tube over the drill such that I would not fall through when the hole is drilled. This is to avoid damage to the bearings. Remember you can not take this apart. You have to drill the hole with the fan in place.

Slide a plastic tube over the drill to prevent it from falling through when the hole is done.

It's a good idea to do this with 2 people. One holding a vacuum cleaner hose and the other one drilling. The suction from the vacuum cleaner will prevent small aluminum pieces from getting into the fan electronics and motor coils.

The hole is in place. The axle will no longer hit the aluminum case. In addition you have now a possibility to put a small drop of oil onto the axle before installing everything again.

Zero thinkpad fan noise

The result is stunning. This is not just a reduction of fan noise. There is no more fan noise at all. You hear sometimes a bit of wind noise when the fan is running a higher speeds but the rrrrrrrrh sound is totally gone.

Thinkpad t60 and t61 fans

Those t60 and t61 fans have a very similar design as the fan of the t43 but they can not be fixed the same way. The t60 fan has no air gap between fan axle and aluminum fan case. All that space is filled with plastic to mount the fan to the case. The actual brass bearing sits right on a hard plastic disk, the axle is shorter and it pushes against that disk. It can however generate the same noise but only if it is not greased properly. Thus do not drill a hole into the t60 fan. You would ruin it. The t60 fan can be detached from the heatsink (the t43 fan can not be detached) and after pulling out the rotor you put some clear syntetic grease and a drop of syntetic oil. This will fix the t60 fan. The t60 is never as loud as the t43 fan since the axle hammers on the plastic disk and that is a softer surface than the metal case of the t43 fan. The noise is therefore less and a bit of synthetic grease (not white grease please) is enough to make it go away.

Another important reason why you can not drill a hole into the t60 fan is that the permanent magnet ring inside the rotor is wider. In the case of the t43 fan the rotor centers itself at the right hight. The the small magnet ring of the t43 fan wants to sit in-front of the iron core of the coils. If you push it down then it will come by itself back up. If you pull it up then it will go by itself down. The magnet of the t60 magnet is wider. It will not come up by itself if you push it down because a section of the much wider magnet is still in-front of the coils iron core.

© Guido Socher, guidosocher at gmail.com, ->back to the main t43p article