The three pin plugs I found at the electronics shop.
When I was reviewing the coolers for our recent Cooler Roundup, I was careful not to run the higher speed fans directly from the motherboard headers. The ever-popular 38CFM Delta fan is not only annoyingly loud at 46.5dBA, but it also draws 0.32Amps and 3.84Watts of power. To avoid blowing the fan headers built into the motherboard these fans come supplied with a 3 pin-to-molex connector, which allows the fan to draw power directly from the computer’s power supply.
However, many CPU cooling fans are supplied with a third wire for RPM monitoring, and if the power is taken directly from the molex connector, this RPM monitoring is not possible. Not only is the RPM rating nice to know, but many system monitoring programs - like MBM - can set alarms, or shut down your system if the RPM drops below a certain threshold, or if the fan fails for more than a few seconds.
The solution is fairly simple; create an adapter that splits the third RPM monitoring wire from the two power supply wires. This will allow the motherboard to track the status of the fan, but will also draw power directly from the power supply. While the theory is fairly straight forward - for someone with my limited electronics knowledge and soldering skills - putting it into practice may be a little more difficult.
The first step was to find some additional 3-pin connectors - the male and female type that the fan adapters use. A quick trip down to the local electronics shop - and after showing the sales assistant what I wanted - I was able to find a number of suitable plugs.
The plugs cost all 60c each for the female type (which included the small metal inserts) and 15c each for the male type. To complete the rest of the set-up, a few lengths of wire, some heat shrink and a soldering iron and solder are all that is required.
Before you start soldering the wires in place, make sure that you connect everything in the right order. I first soldered the wires onto the male connector and used a three-pin fan so that I could tell which wires were for the power and which was the RPM monitoring (In the diagram below Red and Black are for power and Blue/Yellow for RPM). The plugs are quite small, but even for someone with my limited soldering skills, I managed to connect the wires with no big problem.
Cliff - of FanBus fame - has a nice Soldering Guide posted on his website for those of us who are not quite practiced enough with their soldering skills. As you can see in the picture below I first applied some solder to the pins as well as the end of the wires attaching them together.
When the three wires were soldered to the male connector the RPM wire was soldered into a female plug, and the two power wires soldered attached to their own separate plug. Dripping a small amount of solder into the metal inserts ensued that the wires stayed in place. The metal inserts were then slipped into place.
I used some heatshrink to tidy everything and ensure that none of the wires shorted. A couple of cable-ties were used to secure the wires more firmly - the purchased plugs were not as solid as the ones supplied with fans and I wanted to be careful that I didn’t accidentally rip the wires out.
75c, half an hour and one burnt finger later (I really need one of those little alligator clip holder thingy’s) and my fan RPM and power splitter was complete. One end attaches to the motherboard header for RPM monitoring and the second end plugs into the pass-through molex connecter to power the fan.
If I’m ever game to attempt
another Monster Heatsink Roundup, next time I’ll be able to report
the RPM output of each fan - while still drawing power directly
from the power supply.
 21-Cooler SocketA Roundup |
 Chipset Cooler Comparison |
 MacPower DigiDoc 5 |