I would like to salvage these three fans
========================================

They come from an Apple iMac 17-Inch "Core 2 Duo" 2.0 (Late 2006 - iMac5,1 - A1208 - 2114)

CPU Fan
-------

**Apple Service Source P/N:** 922-7641  

**Apple P/N (on sticker):** 603-8690  

**Manufacturer P/N:** BFB0712VHD  

**Voltage rating:** DC12V 0.5A

[![iMac A1208 CPU Fan](https://i.stack.imgur.com/neAmt.png)](https://i.stack.imgur.com/neAmt.png)

| Cable color | On board labels (under sticker) |
| --- | --- |
| Black/Grey | VCC |
| Grey | O/P |
| Black | GND |
| Brown | VIN |

Hard Drive Fan
--------------

**Apple Service Source P/N:** 922-7063  

**Apple P/N (on sticker):** none  

**Manufacturer P/N:** BFB0612HB  

**Voltage rating:** DC12V 0.32A

[![iMac A1208 Hard Drive Fan](https://i.stack.imgur.com/LNzMS.png)](https://i.stack.imgur.com/LNzMS.png)

| Cable color | On board labels (under sticker) |
| --- | --- |
| Black/Grey | Unreadable |
| Grey | Unreadable |
| Black | Unreadable |
| Brown | Unreadable |

Optical Drive Fan
-----------------

**Apple Service Source P/N:** 922-7062  

**Apple P/N (on sticker):** 620-3335  

**Manufacturer P/N:** BG0801-B045-000  

**Voltage rating:** DC12V 0.5A

[![enter image description here](https://i.stack.imgur.com/cBkWv.jpg)](https://i.stack.imgur.com/cBkWv.jpg)

| Cable color | On board labels (under sticker) |
| --- | --- |
| Black/White | SC |
| Grey | S |
| Black | - |
| Brown | + |

Information gathering
=====================

Querying on search engines I found some matching part numbers, but none of the results gave me an accurate answer.

I found some information about other iMac fans, an older [iMac G5 17''](https://www.tonymacx86.com/threads/ersterhernds-imac-g5-isight-17-project.124456/#post-760061), a [newer 27'' iMac](https://www.tonymacx86.com/threads/2011-imac-fan-pinout.215172/#post-1825588) as well as an unknown Apple [Logic Board pinout](https://pinoutguide.com/Motherboard/apple_fan_connector_pinout.shtml). From there I learned more about [computer fans](https://en.wikipedia.org/wiki/Computer_fan_control#Fan_connectors), and PWM controlled fans [4-wire Intel specs](https://web.archive.org/web/20110726062453/http://www.formfactors.org/developer/specs/4_Wire_PWM_Spec.pdf).

All of that points me to guess that they are PWM controlled. All of them are labeled 12V DC and follow the same cable color convention.

| Cable color | Pinout |
| --- | --- |
| Black w. stripe | PWM input signal |
| Grey | Tachometer PWM output signal |
| Black | - |
| Brown | + |

Having understood what PWM is, how it works, and based on what I have been reading, it's clear to me that to drive them from the [GPIO pins](https://raspberrypi.stackexchange.com/questions/298/can-i-use-the-gpio-for-pulse-width-modulation-pwm) of a Raspberry Pi, I need the specs to be able to generate the correct signal. The same applies to read the tachometer signal.

BTW, I also understood that I must get an oscilloscope.

Testing
=======

From what I've learned, without any specs, neither a scope, I decided to test with different voltages on PWM cable.

CPU Fan
-------

| PWM cable Vin | Fan behavior |
| --- | --- |
| 0V | Blades don't move |
| 3.3V | Blades try to spin but can't start |
| 5V | Blades spin fast |

Once fan is spinning

| PWM cable Vin | Fan behavior |
| --- | --- |
| 5V | Blades spin fast |
| 3.3V | Blades spin slow |
| 0V | Blades stop |

HD Fan
------

| PWM cable Vin | Fan behavior |
| --- | --- |
| 0V | Blades try to move and keep trying regularly |
| 3.3V | Blades start spin slow |
| 5V | Blades spin fast |

Once fan is spinning

| PWM cable Vin | Fan behavior |
| --- | --- |
| 5V | Blades spin fast |
| 3.3V | Blades spin slow |
| 0V | Blades spin slower |

ODD Fan
-------

| PWM cable Vin | Fan behavior |
| --- | --- |
| 0V | Blades don't move |
| 3.3V | Blades start spin slow |
| 5V | Blades spin fast |

Once fan is spinning

| PWM cable Vin | Fan behavior |
| --- | --- |
| 5V | Blades spin fast |
| 3.3V | Blades spin slow |
| 0V | Blades stop |

I tried to measure voltage on the tachometer cable with a very basic multimeter without success, but setting it on the continuity test, I can hear it beeping faster or slower depending on the Vin supplied.

Are those tests safe for the fans?  

Is there a way to know the specs without a scope?  

Can I use the fans with relays forgetting about PWM?  

Without specs, is there a way to try to read the tachometer without harming the GPIO on the [Raspi](https://raspberrypi.meta.stackexchange.com/questions/54/what-abbreviation-should-we-use) board?

UPDATE 27/02/2021:
==================

I've been thinking that, since I've the logic board, it should be possible to know what components are involved to power the fans, and it would be even better, if I have the schematics. I searched, and I found the schematics of [some Apple devices](https://schematic-x.blogspot.com/2018/04/apple-schematics-pack.html). The schematics of "APPLE IMAC G5 A1058 ISIGHT M38 DVT MLB - 051-6949 - REV 09 11.16.05.rar" logic board use exactly the same fans that I'm using.

CPU Fan
-------

[![CPU Fan connector logic board schematics](https://i.stack.imgur.com/Fuivg.jpg)](https://i.stack.imgur.com/Fuivg.jpg)

Hard Drive Fan
--------------

[![HD Fan connector logic board schematics](https://i.stack.imgur.com/pFkRG.jpg)](https://i.stack.imgur.com/pFkRG.jpg)

Optical Drive Fan
-----------------

[![Optical Drive Fan connector logic board schematics](https://i.stack.imgur.com/8RW2F.jpg)](https://i.stack.imgur.com/8RW2F.jpg)

I'm using the original [iMac A1208 power supply](https://apple.stackexchange.com/questions/133107/a1208-2006-intel-imac-power-supply-power-good-voltage/134369) to power them.

Logic board power supply connector
----------------------------------

[![Logic board power supply connector schematics](https://i.stack.imgur.com/ToJV4.jpg)](https://i.stack.imgur.com/ToJV4.jpg)

The point of all of this is to replace the faulty main board with a Raspi in order to reuse it as a kitchen computer.

Also, it serves me as a playground to learn electronics, as of, to other people looking for information to reuse iMac parts. :)

I also plan to reuse the temp sensors. I will gather more info and update this post.

Having not enough knowledge about electronics to understand those schemas, now I'm asking: **With these schemas, can somebody tell me the working PWM values to safely drive the fans and read their tachometers with a Raspi?**

By now I did some testing, and I'm sure I can drive them with relays switching between 0V, 3.3V and 5V. Didn't make any tests yet to read the tachometer.