[SOLVED] Case fans not spinning

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70marom

70marom

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Jan 3, 2020
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Hey, I bought a new MB 3 months ago. I’m using the same case with the same fans. Only yesterday I realized that the fans are not spinning.
I have 2 fans with 3 pin connector. On my motherboard I have only 4 pin connectors so 1 fan is connected to 4 pin, and one with molex.
In my gigabyte bios I can see in 5 smart fan (something in bios) my cpu fan and he is RPM and sys fan 1 and sys fan 2 with RPM 0.
 
Solution
Karadjgne
If your current fans are dead, yes, new fans in a new case will work. But I'd still test the old fan to guarantee that is the issue. It is possible to turn off fans in bios, but that would only affect the motherboard, not a direct hookup to the fan from psu - molex.

The only way I can see any different is if the fans are not actually hooked up to the motherboard, but by molex through some sort of controller box/hub that's gone bad. That can be connected to the motherboard for rpm readings, but be powered by a molex plug since it's kinda wierd that 1 fan would be molex and another stock fan would be 3 or 4 pin fan header.
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70marom said:
Hey, I bought a new MB 3 months ago. I’m using the same case with the same fans. Only yesterday I realized that the fans are not spinning.
I have 2 fans with 3 pin connector. On my motherboard I have only 4 pin connectors so 1 fan is connected to 4 pin, and one with molex.
In my gigabyte bios I can see in 5 smart fan (something in bios) my cpu fan and he is RPM and sys fan 1 and sys fan 2 with RPM 0.
Click to expand...
The fan connected to Molex should be running full speed all the time, if not either fan or it's power connection is not good.
3 pin fans should work fine from 4 pin header but you may have to change that header in BIOS to Voltage regulated instead of PWM.
 
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CountMike said:
The fan connected to Molex should be running full speed all the time, if not either fan or it's power connection is not good.
3 pin fans should work fine from 4 pin header but you may have to change that header in BIOS to Voltage regulated instead of PWM.
Click to expand...
I don’t know how to change it...
And both the molex and the 3 pin not working.
 
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CountMike said:
Look in mobo's manual how to change that. Don't know why Molex one is not working, it should turn on as soon as computer is started, maybe try another Molex ?
Click to expand...
The molex fan has a female and male connectors, I connected a male molex from PSU to the female molex connector fan. Is it right?
 
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CountMike said:
The fan connected to Molex should be running full speed all the time, if not either fan or it's power connection is not good.
3 pin fans should work fine from 4 pin header but you may have to change that header in BIOS to Voltage regulated instead of PWM.
Click to expand...
I changed it to Voltage. nothing happened.
 
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It is POSSIBLE that the high temperatures in the CPU chip are because the CPU cooling fan, even though it is working, has only HOT air to work with inside the case, because the case fans have failed.

It certainly appears that both of those 3-pin case fans are faulty. There are a couple of similar and simple further tests you can do for that.
1. Can you get access temporarily to a 12 V automobile battery? Use a pair of light wires to connect each fan to the car battery. Look at the three wires from the fan motor. Normally they will be BLACK on one end (Ground), RED in the middle (+ 12 VDC), and YELLOW on the other end (do not use for this). Connect the fan BLACK to the SMALLER terminal of the car battery (negative), and the RED of the fan to the larger battery terminal (+). The fan should start and run fast immediately.

2. If you cannot get to a car battery but can get a 6 V large lantern (flashlight) boxy battery, you can do the same test. The battery will have + and - terminals labelled. Connect that to each fan. The fan should start up OK but it will not run fast.

If those tests prove the fans are faulty, they need to be replaced. On the other hand, if the fans test well, you may have another problem. Then you should tell us the maker and model nunber of your new mobo so we can look at its manual and advise.
 
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Paperdoc said:
It is POSSIBLE that the high temperatures in the CPU chip are because the CPU cooling fan, even though it is working, has only HOT air to work with inside the case, because the case fans have failed.

It certainly appears that both of those 3-pin case fans are faulty. There are a couple of similar and simple further tests you can do for that.
1. Can you get access temporarily to a 12 V automobile battery? Use a pair of light wires to connect each fan to the car battery. Look at the three wires from the fan motor. Normally they will be BLACK on one end (Ground), RED in the middle (+ 12 VDC), and YELLOW on the other end (do not use for this). Connect the fan BLACK to the SMALLER terminal of the car battery (negative), and the RED of the fan to the larger battery terminal (+). The fan should start and run fast immediately.

2. If you cannot get to a car battery but can get a 6 V large lantern (flashlight) boxy battery, you can do the same test. The battery will have + and - terminals labelled. Connect that to each fan. The fan should start up OK but it will not run fast.

If those tests prove the fans are faulty, they need to be replaced. On the other hand, if the fans test well, you may have another problem. Then you should tell us the maker and model nunber of your new mobo so we can look at its manual and advise.
Click to expand...
Paperdoc said:
It is POSSIBLE that the high temperatures in the CPU chip are because the CPU cooling fan, even though it is working, has only HOT air to work with inside the case, because the case fans have failed.

It certainly appears that both of those 3-pin case fans are faulty. There are a couple of similar and simple further tests you can do for that.
1. Can you get access temporarily to a 12 V automobile battery? Use a pair of light wires to connect each fan to the car battery. Look at the three wires from the fan motor. Normally they will be BLACK on one end (Ground), RED in the middle (+ 12 VDC), and YELLOW on the other end (do not use for this). Connect the fan BLACK to the SMALLER terminal of the car battery (negative), and the RED of the fan to the larger battery terminal (+). The fan should start and run fast immediately.

2. If you cannot get to a car battery but can get a 6 V large lantern (flashlight) boxy battery, you can do the same test. The battery will have + and - terminals labelled. Connect that to each fan. The fan should start up OK but it will not run fast.

If those tests prove the fans are faulty, they need to be replaced. On the other hand, if the fans test well, you may have another problem. Then you should tell us the maker and model nunber of your new mobo so we can look at its manual and advise.
Click to expand...
I don’t have those kind of batteries...
 
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Regular 9v battery works wonders. Just run a wire from red pin to ' + ' and the black to ' - '.

If the fans fail to turn, bad fans. That would be my guess as a psu molex is 12v rail, which also powers the cpu and gpu. Which obviously works. And also powers the motherboard fans.
 
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Karadjgne said:
Regular 9v battery works wonders. Just run a wire from red pin to ' + ' and the black to ' - '.

If the fans fail to turn, bad fans. That would be my guess as a psu molex is 12v rail, which also powers the cpu and gpu. Which obviously works. And also powers the motherboard fans.
Click to expand...
I’ll search for a 9v battery
My molex cable is a long cable with few connectors, in this cable the molex connector connected to the fan and there is another connector that connected to my hdd
My psu has 2 8-pin, connected with he is own cable
And same about the cpu, 6-pin

and BTW my mobo is Aorus B450 M
 
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For both fans to stop dead, both the psu AND the motherboard must have developed issues at the same time. But the motherboard gets power from the 20+4pin, where the 12v joins the rail, and the molex gets power from the 12v rail. The cpu gets power from the 20+4pin and the 12v rail.

There's just too many branches on that tree alive for the trunk to be dead. Far easier to think that 2 fans from the same batch went bad in the same time frame. Just like replacing a headlight or blinker, usually won't be long you replace the other side too.
 
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Karadjgne said:
For both fans to stop dead, both the psu AND the motherboard must have developed issues at the same time. But the motherboard gets power from the 20+4pin, where the 12v joins the rail, and the molex gets power from the 12v rail. The cpu gets power from the 20+4pin and the 12v rail.

There's just too many branches on that tree alive for the trunk to be dead. Far easier to think that 2 fans from the same batch went bad in the same time frame. Just like replacing a headlight or blinker, usually won't be long you replace the other side too.
Click to expand...
And if I’ll buy a new case with new fans? It’s should work
 
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If your current fans are dead, yes, new fans in a new case will work. But I'd still test the old fan to guarantee that is the issue. It is possible to turn off fans in bios, but that would only affect the motherboard, not a direct hookup to the fan from psu - molex.

The only way I can see any different is if the fans are not actually hooked up to the motherboard, but by molex through some sort of controller box/hub that's gone bad. That can be connected to the motherboard for rpm readings, but be powered by a molex plug since it's kinda wierd that 1 fan would be molex and another stock fan would be 3 or 4 pin fan header.
 
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Solution
Karadjgne said:
If your current fans are dead, yes, new fans in a new case will work. But I'd still test the old fan to guarantee that is the issue. It is possible to turn off fans in bios, but that would only affect the motherboard, not a direct hookup to the fan from psu - molex.

The only way I can see any different is if the fans are not actually hooked up to the motherboard, but by molex through some sort of controller box/hub that's gone bad. That can be connected to the motherboard for rpm readings, but be powered by a molex plug since it's kinda wierd that 1 fan would be molex and another stock fan would be 3 or 4 pin fan header.
Click to expand...
WTF
I just opened my pc, turned off the PSU and I disconnected to AC cable
the molex fan is spinning
somehow
I think he always was spinning and I didn’t realized it
so only the 3pin fan is not working
And I don’t think this fan is doing something because now I’m putting my hand near the fan and I don’t fell anything
 
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