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PC Fan Speed Issue

Ears and Eggs

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I have been having this strange problem with the CPU fan on my PC lately. Right from boot I get an error message "0135: Fan Failure" and the fan immediately speeds up to maximum speed. No matter what I do it will stay at full speed for as long as the PC is on. I have been monitoring the system temperature with Open Hardware Monitor and the CPU temperature always hovers in the mid 30C range, never getting really high. Today I unplugged both the Case Fan and the CPU Fan from the motherboard and swapped them around. Now the case fan will rev up to full speed. Seems to be a problem deeper than the fan itself. In the scheme of things it doesn't really prevent me from doing anything with the PC, but that sound sure is annoying lol. System is a Lenovo M91p full tower desktop.

Error message and some system specs below.



IMG_20181105_161729282.jpg
 

Cyparagon

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Do the fans have 2 wires, 3 wires, or 4 wires? Do you have an oscilloscope, a bench power supply, and a pwm/pulse generator/signal generator?

If you've ruled out the fan itself, it is likely a tachometer reading failure, due to either a bad IC, cold solder joint, or open trace.
 

brendon7358

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It's probably the fan header on the motherboard. What motherboard do you have? You can try getting a fan controller and just controlling your Cpu fan from that. Some motherboards will allow you to do it through the bios but it just depends. However some boards will not boot if nothing is connected to the Cpu fan header so you might need to put a dummy load on it or something.

Edit, looks like your motherboard is about $30 on ebay. I promise you, changing it out isn't as difficult as it may seem.
 

Benm

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Maybe, the problem could also be in the fan.

Many such fans have a feedback wire that tells the actual RPM back to the motherboard. This serves several purposes, one of the is ability to tell if the fan is actually still turning and could possbibly turned down even further to reduce noise. It can also be used to detect a hardware fault with the fan (like something getting caught in there blocking it from spinning) at which point the system may refuse to start at all to avoid potential overheating.

What actually happens when the feedback signal is absent or corrupt depends on the motherboard: some will not boot at all, some may reduced at much reduced speed, and some may just power the fan to full power and chug along. The latter isn't even that bad an idea since you an boot most machines with a cpu or case fan that has failed, and then rely on the cpu's thermal sensors to avoid damage to the cpu. That's assuming the heatsink is still on there and just the fan has failed, at which point a system can still run albeit at very low speed.
 

Ears and Eggs

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Do the fans have 2 wires, 3 wires, or 4 wires? Do you have an oscilloscope, a bench power supply, and a pwm/pulse generator/signal generator?

If you've ruled out the fan itself, it is likely a tachometer reading failure, due to either a bad IC, cold solder joint, or open trace.

Unfortunately I do not have those pieces of equipment to test with. The fans have 4 wires.


It's probably the fan header on the motherboard. What motherboard do you have? You can try getting a fan controller and just controlling your Cpu fan from that. Some motherboards will allow you to do it through the bios but it just depends. However some boards will not boot if nothing is connected to the Cpu fan header so you might need to put a dummy load on it or something.

Edit, looks like your motherboard is about $30 on ebay. I promise you, changing it out isn't as difficult as it may seem.

^Yeah that's it. Yeah, I looked through the BIOS settings but there are very limited options with this motherboard. There don't seem to be any options relating to the fans.

I will try plugging the CPU fan into the case fan header again, but this time just leave the case fan unplugged and see if it will let me boot like that.
 

brendon7358

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Unfortunately I do not have those pieces of equipment to test with. The fans have 4 wires.





^Yeah that's it. Yeah, I looked through the BIOS settings but there are very limited options with this motherboard. There don't seem to be any options relating to the fans.

I will try plugging the CPU fan into the case fan header again, but this time just leave the case fan unplugged and see if it will let me boot like that.
If you aren't going to have a case fan leave your case open or something so it doesn't get too hot in there
 




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