Graphic card fan mod & wiring

[HunterSailor]

Greetings

I want to connect a case fan to a graphic card directly to its PCB. I have Sapphire 7870 with dual fans.(Image attached) and the fans connected to its PCB has 4 pintouts (Image attached) whereas a regular case fan [LED/or not] has three pinouts (Image attached). Will it work if i splice the case fan wires to the graphic card fan connectors and if it's possible what wires do i need to connect considering the pinout differences and also what are the pros and cons?What about the specification of the fans, do i need to match the specifications of the graphic card fan i.e. DC 12V 0.35Amp?

[Enderman]

Are you trying to replace the fans on your GPU?

Or add a third fan?

Because it's not recommended to add more fans than the stock ones because the GPU fan control circuitry is only designed for the two fans on the shroud and adding more could risk damage due to too much current draw.

[HunterSailor]

19 minutes ago, Enderman said:

Are you trying to replace the fans on your GPU?

Or add a third fan?

Because it's not recommended to add more fans than the stock ones because the GPU fan control circuitry is only designed for the two fans on the shroud and adding more could risk damage due to too much current draw.

I want to replace the old fans. Apologies for not being clear. I want to replace the two old fans with a new set of case fans.

[mariushm]

12v 0.35a is the maximum amount of energy the fan is going to use (at 100% speed)

The fan has four wires which are ground, voltage (12v) , rpm sensor and pwm (chip on card sends a signal through this wire which tells a chip on the fan to adjust the speed of the fan)

The case fan has only 3 wires, ground voltage and rpm sensor. It has no pwm wire, which means the video card may not be able to adjust the fan's speed (it would always be at 100%). You can connect the case fan without the 4th wire without any problems (except potential lack of speed control)

 

The video card should support slightly more powerful fans, but you shouldn't go overboard. I'd say fans with up to 12v 0.5A should be fine but unless you want the fans to be always at 100% speed, you should use fans with 4 wires.

Of course, you can safely use fans that use less power (less than 0.35A)

 

Case fans and video card fans should have the wires in the same order, so you could just cut the wires somewhere close to the connector and solder the wires of the old video card connector to the case fan wires.

 

Keep in mind that a lot of video cards have in the firmware (bios) a fan profile .. ex they know that the fan will move 30 cubic feet of air at 100% speed and only 10 cubic feet of air at 25% speed ... and knowing that and knowing how efficient the heatsink is , they can estimate at which percentage they should run the fan when the video card reaches some temperature.  For example, if the card is less than 60c hot, the card may keep the fan at 25% speed, and when it goes above 70c the card may raise the fan speed to 50%.

However, if you install a fan that moves a way different amount of air, the percentages won't be the same and the card could overheat by not raising the fan speed enough.

 

[HunterSailor]

28 minutes ago, mariushm said:

12v 0.35a is the maximum amount of energy the fan is going to use (at 100% speed)

The fan has four wires which are ground, voltage (12v) , rpm sensor and pwm (chip on card sends a signal through this wire which tells a chip on the fan to adjust the speed of the fan)

The case fan has only 3 wires, ground voltage and rpm sensor. It has no pwm wire, which means the video card may not be able to adjust the fan's speed (it would always be at 100%). You can connect the case fan without the 4th wire without any problems (except potential lack of speed control)

 

The video card should support slightly more powerful fans, but you shouldn't go overboard. I'd say fans with up to 12v 0.5A should be fine but unless you want the fans to be always at 100% speed, you should use fans with 4 wires.

Of course, you can safely use fans that use less power (less than 0.35A)

 

Case fans and video card fans should have the wires in the same order, so you could just cut the wires somewhere close to the connector and solder the wires of the old video card connector to the case fan wires.

 

Keep in mind that a lot of video cards have in the firmware (bios) a fan profile .. ex they know that the fan will move 30 cubic feet of air at 100% speed and only 10 cubic feet of air at 25% speed ... and knowing that and knowing how efficient the heatsink is , they can estimate at which percentage they should run the fan when the video card reaches some temperature.  For example, if the card is less than 60c hot, the card may keep the fan at 25% speed, and when it goes above 70c the card may raise the fan speed to 50%.

However, if you install a fan that moves a way different amount of air, the percentages won't be the same and the card could overheat by not raising the fan speed enough.

 

So if i use fans that match the current graphic card fan specifications, even though they will always run on 100% speed at that given rating. Also keeping in mind that it draws the same amount of air or slightly more than the current fans, then I'm good to go?

There are no 80mm LED fans with PWM control, right?

[Enderman]

9 hours ago, titaniumshield said:

I want to replace the old fans. Apologies for not being clear. I want to replace the two old fans with a new set of case fans.

Ok then you need 12v fans that are 0.35A or less, they need to be 4 pin if you want then to not run a 100% all the time, and yes you can cut the connector off the old fans and solder it to the new fans. Just don't get the cable colours mixed up.

[HunterSailor]

The only problem is there are no 80~90mm fan with the same specification. I can use old socket 775 Intel stock fan which will provide PWM control but they are rated at 0.60A which is risky. Or i can use a 90mm fan rated at 0.25~0.28A and just fan the air flow will be enough for the graphic card.

I'm stuck.