Left fan spins full speed at startup since logicboard repair



Since having my logicboard repaired following a no-boot-at-all problem, my left fan spins like crazy from startup. Right fan appears normal.


1) Left fan starts at startup (i.e. as soon as power button is pressed).

2) iStats Menu indicates:

a) left fan 0 rpm (but left fan is spinning at top speed, opened MBP to check)

b) right fan 1998 rpm (normal)

c) Overall temperature 30 deg C (GPU heatskink 35 deg C, Heatskink A 33 deg C, Heatskink B 30 deg C, all other readings about 30 deg C)

3) Apple Hardware Test (done twice) reads:

Alert! Apple Hardware Test has detected an error.

4MOT/1/40000002: Left side-0

Pass Number: 1

Total Time Testing: 2mins 55 secs


PRAM, NVRAM and SMC reset - No change.


Any suggestions as to what might be the problem and how to fix it? Hardware or software? Are there any other tests to do to determine the cause?

Thanks in advance,


Answered! View the answer I have this problem too

Is this a good question?

Score 0
Add a comment
Spread Fixmas Cheer
Get $12 off your purchase of $50 or more with code FIXMAS12
Spread Fixmas Cheer
Get $12 off your purchase of $50 or more with code FIXMAS12

1 Answer

Chosen Solution

Take it back to whomever did the repair and request a fix or a refund.

Was this answer helpful?

Score 2


A web search for your error reveals no solution. If you had this repaired at an Apple Store it should at least be covered for a couple of months. If so I would contact Apple and they will FEDEX you a shipping box. Turn around is usually four days anywhere in the world. In Belgium it's: Belgium

Flemish: (32) 070 700 772

French: (32) 070 700 773




Hi Mayer,

Thanks for the input. Do you mean to say that my fan problem is hardware related? Is your answer based on experience or a simple guess?

Just for you info, I live in Belgium and the the logic board was fixed in the USA. Sending it back neither a cheap nor the easiest solution, therefore, iFixit being a DIY website, I'm hoping to find a DIY fix if possible.




To check to see if it's not hardware related, just boot up from a system installation disk. If the fan problem goes away it's software, if it stays, it's hardware.


Just received a message from the repair shop. They claim the fan, which has an inbuilt regulator, is failing.

I opened the MBP, disconnected both fans, connected the right to the left and it appeared much more silent. I have therefore ordered a new fan.

I will post the result as soon as the new fan's installed.

Thanks none the less for your feedback.



PS: Gave the installation DVD away so can't run your check. Besides, would the test tell me if it's a logicboard or fan hardware problem?


The original installation disk contains diagnostics that can be accessed by starting and holding down the "D" key. See if you can get it back as the system can't be installed on another model Mac.


Show 1 more comment

Add a comment

Add your answer

Ken will be eternally grateful.
View Statistics:

Past 24 Hours: 1

Past 7 Days: 1

Past 30 Days: 12

All Time: 2,095