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I'm trying to put a new CPU cooler in my 1999 IBM Aptiva 2163-580 (which has an Intel 440BX chipset, in case that's relevant). The system uses a Slot 1 CPU.

The old cooler had a 2-pin connector, which mated exactly with the connector on the system board:

Old Slot 1 CPU with fan that uses 2-pin connector

The new cooler, on the other hand, has a 3-pin connector, which doesn't match the connector on my system board:

New Slot 1 CPU with fan that uses 3-pin connector

How can I connect this new fan to my system and make it work?

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As per the other answer, in your case the yellow wire is not needed - it's a tacho signal that shows the current fan speed.

It is possible to physically plug the new fan into the old connector with only the red and black wires connecting to the board. However the pinout of the fans are not compatible at the moment - the red and black wires are reversed which will not function correctly.

Fortunately KK connectors can be dissassembled relatively easily. If you use a small jewelers flat head screwdriver (or some other similar object), and gently press down on the metal latches in the slots on the side of the plastic connector housing, the wires should pull out.

You can then either swap the red and black wires over in the 3-way connector, or preferably plug them in to the old two-pin housing. If using the latter option, the yellow wire can simply be cut off or wrapped in insulation tape.

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Just plug it in, making sure the red and black wires are the ones on the pins. The connector should be keyed to enforce this. The yellow wire is for monitoring the fan's speed, and isn't required for normal operation.

You may need to swap the wires around if the keying doesn't match. This is simple enough: the connectors are held in place by small springs, which can be released by pressing down on them through the side of the connector with a small screwdriver or similar, while pulling on the wire.

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    In some cases (I'm not familiar with this particular IBM model) you need to disable fan monitoring in the bios or you'll get "fan doesn't work" errors on every boot. I have even seen computers that refused to boot, only let you in the bios, if the fan error was detected. – Tonny Sep 18 at 12:03
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    @Tonny Correct me if I'm wrong, but shouldn't that only happen if the board is expecting 3 pins? In this case there should be no difference detectable for the board, since it cannot detect the fan speed in the first place. – Kakturus Sep 18 at 12:44
  • @Tonny Kakturus is correct; this can actually be done either way (2-pin fan on 3-pin board, or 3-pin fan on 2-pin board) and work in the sense that the fan will run, but a 3-pin board will think the fan is stopped and invoke safety measures while a 2-pin board will be completely unaware. – smitelli Sep 18 at 13:35
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    Beware! The pinout of the 2-pin fan and the 3-pin fan in terms of keying do not match in this case. Simply plugging it in will connect the fan with reverse-polarity. – Tom Carpenter Sep 18 at 14:20
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    If the polarity is a problem (the fan runs backwards) you can pull the wires from the plug housing by pressing down the metal tags with a screwdriver blade or something similar, and swap them over. – alephzero Sep 18 at 14:46

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