[SOLVED]820-2914-B Late 2011 A1297 MBP one fan won't spin

[razorwoods]

I'm working on a late 2011 A1297 17" MBP where one of the fans doesn't spin. The fan will move very slightly back and forth but not spin. The fan is actually good, it seems to be the power going to the fan from the connection on that side. The good side is kicking out 4.2v while the non-working side is only putting out 3.2v . The rest of the laptop works fine. I don't have the board view for this 820-2914-B board so I'm not sure where to look.

Can anyone maybe point me in the right direction and / or if someone has this board view & schematic that would be really nice too.

 

[jgraffis]

do google search for the .brd file. have you tried a different fan yet?

 

[razorwoods]

I was able to obtain the boardview. Yes, the first thing we did was replace the fan thinking it was just a faulty fan. New one did the same thing. So we plugged the original fan into the 2nd fan position and it fired right up like normal. We then tried the other fan in the original position and it had the same non-working behavior. Plus the voltage issue points right at it being something besides the fan.

 

[dukefawks]

4.2V where? Post voltages on all 4 pins.

 

[razorwoods]

I totally misread the initial values since I didn't have the board view / schematics when I initially posted this. Here are the values:
Dead Side
J5650 PINS:
1) 0.0v
2) 3.1v
3) 3.2v
4) GND

Working side:
J5660 PINS:
1) 4.9v
2) 1.67v
3) 0.8v
4) GND

Looks like PP5V_S0 should be sending 5v to J5650 pin 1 , but of course there's nothing happening there.

 

[dukefawks]

Well, pin one should have 5V it is directly connected to 5V_S0. Just run a wire to the nearest 5V_S0 point.

 

[razorwoods]

LOL, too funny... after spending about 20 minutes tracing down and testing various points thats exactly what I did. I'm not the greatest with schematics so I'm sure you would have gotten to the same point in much less time. In the end I simply jumped J5660 Pin 1 to J5650 Pin 1. Both fans are working perfectly now.