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Model A1286. Released February 2011 / 2.0, 2.2, or 2.3 GHz Quad-core Intel Core i7 Processor

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Fans run at full speed intermittently after logic board replace

I just replaced the logic board, and now the fan intermittantly spins up to full speed (7500RPM) even when the computer is cold or just booting up. I was wondering if i maybe didnt get something seated right? or if there may be a bad sensor? I reset the SMC controller and the PRAM, didn't seem to help, but the more I run it, especially getting it up to tempterature, the better it works. So maybe it will fix itself as the heat sink seats itself into position. Just wondering if anyone has experienced this before and if anyone has any suggestions?

Update (11/14/2017)

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The left fan is intermittently running at max speed, but it changes by the second, it will go a few minutes running normally, but then jump up to 7500 for a few seconds and drop back down, all while the right fan never changes, unless the overall temperature of the heat sink increases, then the right one will speed up as expected

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See if this app helps isolate whats happening: TG Pro. Paste a screenshot of the main screen for us to see.

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It appears the right fan is not spinning up at all which is why the left is going full speed to compensate for the failing right fan. Either something is jamming the blades just enough to slow them down or the motor is failing. It's also possible the left fan tach is failing so it thinks it needs to run hard.

I would first see if an SMC reset solves this or try replacing each fan with a spare.

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When I tested it at high temperature, the right fan would kick up to full speed when the temperature of the heat sink required it to, so I believe the right fan is working properly. It could definitely be something with the left fan because its extremely intermittant, it will go from 2000 to 7500 back to 2000 in a matter of seconds, just pulsating up and down whenever it wants. I have tried resetting the SMC a couple times to no avail, I suppose the next thing I can try is to replace the left fan, but it seems to me more like a sensor issue than the fan itself, not sure if that can be replaced.

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J.Morgan Legreid will be eternally grateful.
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