[SOLVED] Got a new mobo and now my fans are stuck at highest setting even while on "auto fan control"??

williamsgarrett868

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Dec 27, 2018
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Hello. I have had an HP p6520y stock desktop since 2010, recently after hitting the 8 year mark, everything has been breaking one by one. My HDD failed, and my mobo bricked out of nowhere. I got a 256GB SSD and a new Gigabyte GA-78LMT-USB3 R2 Mobo, with my old mobo at the PC would boot my fans would go super loud and fast then almost immediately quiet down and run at an automatic speed based on CPU Temps, ever since I got my new mobo put into my PC the fans start up at highest speed and never slow down or quiet down, it is quite obnoxious. I have checked the settings in the bios and confirmed that automatic fan control is enabled based on core CPU temps, but clearly that isn't true. Here is a SS of my Specs from NZXT CAM and my temps and fan speed.
Important Note: The cpu fan is 3 pronged (which works of my stock fan) and the System Fan (CHA_FAN) is 4 pronged, although my system fan wire is only 3 pronged so there is one extra prong always out on that one.



My point is does anyone know what's going on and how I can fix it?
 
You may not be able to change this unless you change some components.

The root of the problem is that it appears from your post that both the CPU cooler and the case vent fan are of the 3-pin type - that is, the connector on the end of their wires has only three holes in it. To control the speed of that type of fan the mobo header used must be able to use the older method called Voltage Control Mode (aka DC Mode). However, the labels on those headers on your new mobo indicate that they cannot do that. Instead, each of those headers can only use the new PWM Mode that is ideal for the new 4-pin fan design, but cannot control the speed of a 3-pin fan.

So what can you do? Two possible routes.

1. Buy two new fans and ensure they are of that new 4-pin type. You would need two slightly different fan models. The one for the CPU cooling needs to be of the "Pressure" type to force air through the narrow gaps between fins of the CPU cooling heatsink. The one for case cooling should be of the "Air Flow" type for maximum air flow against much smaller backpressure. For the CPU cooling system it should NOT be necessary to replace the entire CPU cooler. Usually that system consists of a metal heatsink with fins held tightly against the top of the CPU with thermal paste between for good heat flow, plus a fan fastened on top of the heatsink. The fan VERY often can be removed alone without disturbing the heatsink. Sometimes it is held to the heatsink with screws, sometimes with metal arms or springs. And almost always the size of it is one of the common computer fan sizes like 80mm or 90mm or 120mm. (The size of a fan is the length of one side of the square fan frame.) So examine your CPU cooler system carefully, see if you can figure out how to remove the fan from the heatsink, and check its size. The case vent fan should be much easier to figure out how to replace.

2. Alternatively you can get a device that can convert from the 4-pin PWM signal your new mobo' headers are putting out to the older Voltage Control Mode that your old fans can accept. There are few of these on the market. But one is the Phanteks PWM Hub. It gets power for its fans from the PSU directly via a SATA power output, and picks up the PWM control signal for fan speeds from a cable to the CPU_FAN header. Then it does the conversion and has six ports to plug your fans into. You MUST plug the CPU cooling fan into its marked white Port #1, since that is the only port on the Hub that can send its fan's speed back to the CPU_FAN header. This is important because that header monitors its fan's speed for fan FAILURE. Then the case fan can plug into any other port, but its speed cannot be reported anywhere so you will never "see" it. This arrangement has a small weak point in that it puts the case ventilation fan under control based on the internal temperature sensor of the CPU chip, instead of the sensor on the motherboard, But that's really a small detail not to worry about.

I suspect that the cost of these two options is similar. But consider this also. If several components of your older system have failed, the old fans may also fail soon. So maybe replacing the fans is better than using them with a conversion system.

BEFORE doing either of those, check this detail. Many mobos now use 4-pin headers for all their fans, but in BIOS Setup allow you to change the Mode each header uses to control its fan. The manual for your mobo does NOT say it can do this anywhere, so you may not find that option. But look in BIOS Setup anyway at both of its fan headers and see if there is a choice to make between DC Mode and PWM Mode. IF you can change both headers to DC Mode (Voltage Control Mode) that will solve your problem without changing any components.
 
You may not be able to change this unless you change some components.

The root of the problem is that it appears from your post that both the CPU cooler and the case vent fan are of the 3-pin type - that is, the connector on the end of their wires has only three holes in it. To control the speed of that type of fan the mobo header used must be able to use the older method called Voltage Control Mode (aka DC Mode). However, the labels on those headers on your new mobo indicate that they cannot do that. Instead, each of those headers can only use the new PWM Mode that is ideal for the new 4-pin fan design, but cannot control the speed of a 3-pin fan.

So what can you do? Two possible routes.

1. Buy two new fans and ensure they are of that new 4-pin type. You would need two slightly different fan models. The one for the CPU cooling needs to be of the "Pressure" type to force air through the narrow gaps between fins of the CPU cooling heatsink. The one for case cooling should be of the "Air Flow" type for maximum air flow against much smaller backpressure. For the CPU cooling system it should NOT be necessary to replace the entire CPU cooler. Usually that system consists of a metal heatsink with fins held tightly against the top of the CPU with thermal paste between for good heat flow, plus a fan fastened on top of the heatsink. The fan VERY often can be removed alone without disturbing the heatsink. Sometimes it is held to the heatsink with screws, sometimes with metal arms or springs. And almost always the size of it is one of the common computer fan sizes like 80mm or 90mm or 120mm. (The size of a fan is the length of one side of the square fan frame.) So examine your CPU cooler system carefully, see if you can figure out how to remove the fan from the heatsink, and check its size. The case vent fan should be much easier to figure out how to replace.

2. Alternatively you can get a device that can convert from the 4-pin PWM signal your new mobo' headers are putting out to the older Voltage Control Mode that your old fans can accept. There are few of these on the market. But one is the Phanteks PWM Hub. It gets power for its fans from the PSU directly via a SATA power output, and picks up the PWM control signal for fan speeds from a cable to the CPU_FAN header. Then it does the conversion and has six ports to plug your fans into. You MUST plug the CPU cooling fan into its marked white Port #1, since that is the only port on the Hub that can send its fan's speed back to the CPU_FAN header. This is important because that header monitors its fan's speed for fan FAILURE. Then the case fan can plug into any other port, but its speed cannot be reported anywhere so you will never "see" it. This arrangement has a small weak point in that it puts the case ventilation fan under control based on the internal temperature sensor of the CPU chip, instead of the sensor on the motherboard, But that's really a small detail not to worry about.

I suspect that the cost of these two options is similar. But consider this also. If several components of your older system have failed, the old fans may also fail soon. So maybe replacing the fans is better than using them with a conversion system.

BEFORE doing either of those, check this detail. Many mobos now use 4-pin headers for all their fans, but in BIOS Setup allow you to change the Mode each header uses to control its fan. The manual for your mobo does NOT say it can do this anywhere, so you may not find that option. But look in BIOS Setup anyway at both of its fan headers and see if there is a choice to make between DC Mode and PWM Mode. IF you can change both headers to DC Mode (Voltage Control Mode) that will solve your problem without changing any components.
 

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