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Question

Inspiron 7568 Laptop Fan Will Not Spin

by bruhthakuga / May 29, 2017 11:22 AM PDT

Friends, My Inspiron 7568 Laptop fan will not spin, actually the fan blade spin a couple of revolutions immediately after powering on but that is all. I tried HWinfo, SpeedFan to no Joy.

I took the fan off and bench tested it with 5 volt dc and it work, I reconnected the fan to the mother board and tested the terminals at the "fan side" of the connection and 5vdc is there? The fan is clean and nothing is preventing the fan blades from spinning. This is very flabbergasting ! ! !

This is a four wire fan, Black and Red for power, Yellow for sending the RPM signal to the motherboard and Blue for receiving the speed control signal from the motherboard which is my problem.

The fan always have power to the black and red power terminals, normally the blue terminal controls fan speed with negative five volt pulses, when my laptop is on there is a constant negative voltage at the blue terminal causing the motor to not spin but why?
In BIOS there are no option for fan control however the HWinfo & SpeedFan does show the fan information and indicate zero RPMs but the control to adjust fan speed does not work.

Do anyone have a solution to my DeLemon? Please help.

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All Answers

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Answer
This sadly
by R. Proffitt Forum moderator / May 29, 2017 12:25 PM PDT

Means it needs a new motherboard. Some techs just wire the fan over to some USB port power pin.

It's also been seen that a "tested fan" doesn't spin. I know techs that are flabbergasted when I order a new fan unit and once in a while it fixes it. The cost of the unit means I never try to figure out a 20 buck fan and why it doesn't work.

So there it is. Wire it up or try a replacement. Cheaper than a new mainboard.

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Don't Run A USB Cable To Fan - Cut The Control Wire
by bruhthakuga / May 29, 2017 1:21 PM PDT
In reply to: This sadly

Buying a new fan doesn't make sense when the old one works . . . also to rig it up by running a wire over to powering the fan by USB also doesn't make sense when the fan is getting the proper voltage.

Keep in mind that when the PC is on the motor always has power at it's power terminals, the fan speed is controlled is by the motherboard sending a grounded pulse signal through the blue wire to the motor, the longer the negative pulses are the slower the fan spins and shorter negative pulses allows the fan to spin faster. The motor will not spin with a constant ground to the blue wire or it will spin at top speed with no voltage to the blue wire.

That said the simplest way to RIG THE FAN is to cut the blue wire. . . . . coincidentally just before I got your response that is what I did and now I got full fan, going to not like it in the winter with all that air blowing on me.

Getting a new motherboard is completely out of the question even though I paid a grand for this PC but I am hoping that there is a software solution but until then full fan works.

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I'd had this discussion with techs too many times.
by R. Proffitt Forum moderator / May 29, 2017 1:31 PM PDT

By the time it gets to me they have wasted a day on the job. It's a small job with a big expense most of the time. 150 for the shop counter counter (minimum around here) then the estimate is for a new mainboard and fan. Few will sign up for that so we offer a no-warranty fix with a new fan and if that fails a quick power tap from the USB pins.

There are long other solutions but if you want it to be software, test it with another OS load.

The reason for the +5V tap instead of +12V is to run the fan, but not at full tilt. Seems to work out for most folk.

Post was last edited on May 29, 2017 1:31 PM PDT

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