Laptops forum

Question

Laptop Motherboard Fan wont start

by onlyprinzp / March 9, 2017 7:58 AM PST

When I measure the PIN1 of JP26 with a multimeter I only get about 0.26V instead of 5.0V, for the fan to work.

The U26 chip shows the following readings:

PIN1 - about 5V
PIN2 - about 5V
PIN3 - about 0.26V

If there is somebody who could help a little would be much appreciated!

Thanks in advance!

The fan is not the issue, i hooked it up to 5V and spins like a charm.

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All Answers

Collapse -
Answer
START
by onlyprinzp / March 9, 2017 8:00 AM PST

Hello everybody,

I am new to this board and so I would like to ask a question, maybe somebody can help me.

The problem I am facing is that the fan on my motherboard of my laptop wont start. The strange thing is that first it was working. Then I switched it off and suddenly wont work anymore. ( the fan only ) More strange is that the laptop functions perfectly, just that it get heaten up badly due to the fan issue.

I took out the schematics of the board and found the fan control section shown below:

Collapse -
If you can't replace chips
by R. Proffitt Forum moderator / March 9, 2017 8:03 AM PST
In reply to: START

Let's say you can't find the chips or why. Why not hardwire the fan to a power source and let it run?

That's a lot cheaper than the other fix (new motherboard.)

Collapse -
Hardwire is not an option
by onlyprinzp / March 9, 2017 8:06 AM PST

If I hardwire the 5V of the fan it will go 100% rpm I dont want to listen to that loud cooler the whole time. I d like to find the issue on the MB and fix it. If it is a chip I d like to solder it if necessary.

Collapse -
That's easy to fix.
by R. Proffitt Forum moderator / March 9, 2017 8:12 AM PST

Put a resistor in to drop the fan speed. Beats the new motherboard cost.

As to you wanting to find the cause, you could replace the suspect chips.

Collapse -
Nice
by onlyprinzp / March 9, 2017 8:15 AM PST
In reply to: That's easy to fix.

Ok, but I am really looking forward to find the cause of this issue. I measure the VCC_FAN1 Voltage and it only comes out to 0.26V, I changed already the chip, still the same. Laptop boots but fan not working at all...

Collapse -
Not always the chip.
by R. Proffitt Forum moderator / March 9, 2017 10:23 AM PST
In reply to: Nice

This sort of failure is not always the chip. I've lost count of cracked boards (drops) and for me the fix is the fan to the power source and if too fast, a resistor in the power line to the fan.

These are done only for clients that understand it's a workaround and no warranty given.

Post was last edited on March 9, 2017 10:28 AM PST

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