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Fan wiring question

B

BeavermanA

2[H]4U
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Apr 27, 2006
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Alright I'm going to have 6 fans for two 3x120 rads, instead of having a shit ton of daisy chained 3-pin to molex connectors stuffed in the back of my case, can I just cut and strip all the fan wires and use a wire nut to connect all the yellow, red and black wires and then run them into a single 3-pin to molex adapter?
 
Yes, and no.

Several things you need to know (your adapter may do it for you but I want to make sure you get what you want) the fans red wire just means its the postive wire, there is no requirement it is colored red. Most likely your fans will be +12V.

The red wire in the computers power supply 4 pin molex is +5V, it is the yellow wire that is the +12. So for normal operation the red fan wire will be connected to the yellow wire in a 4 pin molex from the power supply. (on a 3 or 4 pin fan header for the motherboard the yellow is rpm and the red is +12, normally). The point is make sure you know what is going where.

Your other issue is that 6 120mm fans is a pretty decent load on the motherboard fan header. Most of them are able to provide 1.5A (check and see if your mother board manual mentions it anywhere and an email to the manuf tech support might be in order.) 1.5 A @ 12 V is 18W. Your fans should be marked with either the amperage they use or the wattage. Just add them up. 3 fans, maybe 4 is likely all you should put on that motherboard fan header. You can put unlimited fans onto a power supply 4 pin molex. The good news is typically it does not harm the rest of the board if you burn out the motherboard fan voltage supply. A quick search seems to indicate no-one knows for sure and its is not in the manual, check me on that. On the EVGA forums they are throwing around 1A which is 12W but no one can document where that number came from.

You will want to be able to vary the speed vs noise so a fan controller might be a good idea.

Another idea is to use a spdt switch to be able to proivde the fans either 12V for full power cooling or 7V flor low noise web sufing. Google "7v fran mod" basically you hook the fans red wire to +12 and the ground wire from the fan is switched via the switch between black ground which gives full 12V and the power supply red wire which is +5 which then gives the fan 7V for low speed/low noise operation.

Anyway servral options are open. Hooking all 6 to one Motherboard header needs some investigation of total current draw before you do it. You have 5 headers + the cpu. Ask EVGA what the max recommended current/wattage draw is per header and if there is a board total current draw/wattage for all fan headers combined.
 
Got it working, used my plan after opening it up and looking. I was just thinking about this yesterday as it was pretty difficult to stuff all the 3-pin to molex adapters in the back with 3 fans, let alone 6. You're right about the wires, when the red comes out of the 3-pin, it attaches to the yellow on the molex. I cut them all before that and kept the 3-pin in, so just had to match the 3 red and black wires to the same, then plug it into the molex.
Fans are low rpm s-flex fans, not too loud so I can tolerate them without using a fan controller.

I like the terminal block idea too, maybe I'll do that when I have some more time, should be able to find everything in one of the containers at work.

img0572v.jpg
 
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