Fan speed over 6200 rpm on A1278 13 late 2011

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Level 1

8 points

Fan speed over 6200 rpm on A1278 13 late 2011

Hi,

I've got an issue with my MacBook Pro 13 late 2011. The fan connector to the motherboard ripped apart so I soldered it in and it's working now. I replace my hdd with an ssd and all good, clean install of Sierra, working perfectly.

There is only one issue, I have my fan rev at around 7100 rpm:

The issue wasn't caused by the soldering since it revved up before, as well.

I've got a diff app showing:

Can it be an OS issue?

MacBook Pro, macOS Sierra (10.12.6)

Posted on Aug 25, 2017 1:52 AM

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Answer 1

vitalize Author

Level 1

8 points

Aug 25, 2017 5:12 AM in response to ThomasD3

I've soldered the 4 pins connecting the fan to the board as they unpinned a while ago. I've changed the fan and changed the hdd to an ssd.

It's been revving at 7.2k rpm since I turned it on. The plus is that it runs cooler than ever )) but I loose the portability side since it's too loud.

Is there a way to reset the sensors or what can be the issue?

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Answer 2

ThomasD3

Level 1

46 points

Aug 25, 2017 4:02 AM in response to vitalize

The fans will rotate roughly up to 7200 if you program the SMC to run them at full speed.

So, I would guess that the control of the fans is not working and they're running as fast as they can.

The OS limits the speed to 6200 rpm so I think it's outside of software control right now.

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Answer 3

ThomasD3

Level 1

46 points

Aug 25, 2017 5:24 AM in response to vitalize

From what I could find online, the pinout is:

Pin 1: 5V DC

Pin 2: Motor Control (PWM signal)

Pin 3: GND

Pin 4: Tach

Is it possible that you shorted pin 1 and 2? it would be the most likely since the PWM signal would always be high and the fan would run at full speed.

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Answer 4

ThomasD3

Level 1

46 points

Aug 25, 2017 8:43 AM in response to vitalize

Check for a pin1 and pin2 short, I'd bet that's the issue.

The controller outputting the PWM signal on pin2 may not like that line being tied high for long as well, so I would really check that before running the computer for long as if the buffer breaks, the line may end stuck high or low forever afterwards, depending on how it's implemented.

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Answer 5

ThomasD3

Level 1

46 points

Aug 25, 2017 6:13 AM in response to vitalize

Ideally, you should check the PWM pulse on pin 2 with a scope because it would tell you right away if the problem is on the controller / software side, or on the fan's side.

If you don't have the equipment, should check if pin 1 and 2 are bridged with a meter; you can get one for < $10; a visual inspection is often misleading.

This is where I'd start the troubleshooting since it's the most likely problem; but then after that you'll need a way to monitor the pin 2 pulse to do anything more advanced.

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