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BOOSTA on cMP5.1 runs crazy

Hi guys - I have the identical problem - cleaned, reseated and re pasted everything with no change - cannot control boostA fan with any tools either. Did you land a final solution?? Many thanks - Ecca55
 
KeesMacpro - thanks for the feedback. I have swapped out the fan with a spare from another heatsink and the problem remained. So appears that the SMC is damaged or I have a short somewhere?? Do you know the 4 pinouts for the fan and 2 for sensor that plug into the cpu tray?? Ecca55
 
Ecca55 said:
KeesMacpro - thanks for the feedback. I have swapped out the fan with a spare from another heatsink and the problem remained. So appears that the SMC is damaged or I have a short somewhere?? Do you know the 4 pinouts for the fan and 2 for sensor that plug into the cpu tray?? Ecca55
Click to expand...
Hi Ecca55,

I've replaced all fans in the MP 4,1/5,1 by 3rd party fans, except for the CPU fan(s).
The OEM Delta fans for the CPU have an exceptional wide rpm range , so its hard to find an apropiate replacement.
I'm planning on testing some more though, but fact is i havent checked the pinout for the CPU fans yet.

Anyway, the fans are of a Apple 4-pin type , different from a PC 4-pin PWM .
In case you have a multimeter you could check the following on the connector:
pin1- ground
pin2- 12V constant (for a circuit inside the fan)
pin3- Tacho signal
pin4- V variable controlling the rpm
(I just called them 1-4, no pinout related)

In case e.g. the 12V constant is short circuited with the V variable, the fan will run fullspeed , no matter what the SMC dictates.

This way you could at least check if the SMC is still working correctly.

EDIT: as for the case of the OP, the sensor reading was correct, so no sensor fail , you could check with e.g.MacsFanControl if there's a correct sensor reading in your case.
 
Screen Shot 2021-02-20 at 9.56.24 am.png

Thanks - you can see that all the temps are fine, just that BOOSTA is maxed out - regardless of what I do with the custom setting. All other fans respond to any custom changes that I make, but not BOOSTA. I may just drop a pot/resistor into the 5v feed for the fan as a fix.
 
Just a quick update - the BOOSTA fan does spin down when in sleep mode and revs up as soon as out of sleep mode
 
Ecca55 said:
Thanks - you can see that all the temps are fine, just that BOOSTA is maxed out - regardless of what I do with the custom setting. All other fans respond to any custom changes that I make, but not BOOSTA. I may just drop a pot/resistor into the 5v feed for the fan as a fix.
Click to expand...
Ecca55 said:
Just a quick update - the BOOSTA fan does spin down when in sleep mode and revs up as soon as out of sleep mode
Click to expand...

Thx for the updates.

If you decide to make a voltage drop with a resistor, (obviously) the Boost A will not respond to the CPU A Temps anymore, resulting in too high T under (heavy) load or a Boost fan running constantly high...

I'm going to take a look at the fan pinout today and post it.
As a last resort , you could measure the voltage of Vc to be 100% sure the SMC is not working correctly for this fan ...
 
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