No fan RPM on rewired Glaciator

[Len]

I've rewired my Glaciator to run off a modified molex connector at 7v. I separately connected the fan sensor wire to the sensor pin on the motherboard power connector near the CPU socket on my Epox 8K7A expecting to get a fan RPM reading from MBM5 but it reads as 0 rpm. Any idea why? Is the rpm sensor not working because I don't also have the Glaciator powered from the same mb power connector that the rpm sensor is on?

[Diggrr]

The RPM sensor needs the black wire to ground. With the 7 volt mod, it's +5.
You should try using a rheostat on 12 volts to get the sensor working, and the fan slowed down.

[Len]

Is there any other way without using a rheostat? I prefer a fixed 7v connection.

[Silversinksam]

If we can convince you to use a Rheostat Hoot has some real high quality Rheostats for sale in the classified section:

http://forums.overclockers.ws/vb/attachment.php?s=&postid=440623

http://forums.overclockers.ws/vb/attachment.php?s=&postid=440624

(Len its in the Classified>Cooling section)

If you are a new member, I'm sorry but you cant view the classified section just yet, but 100 posts isn't to hard to achive.

Along the way to 100 posts I'm sure you can share some tips or learn some yourself from the many fine and astute members.


PS Im sure if you are a new member and you Shoot Hoot a PM, he might be willing to part with a few of them, just dont expect him to ship first. :p

[plague]

well what if you just ran a wire from the ground pin on the mobo header to the ground wire on the molex? Then the rpm monitor would be grounded, and the fan would still be using 7V.

edit: why would you only want 7V for the glaciator fan?? It's weak enough as it is, and not very loud at all.

[Diggrr]

You could do the math to find what resistor is needed. Then just solder it in the positive line (with protective heatshrink tubing on it).
(12 volts) - (7 volts) / (fan amperage) = Resistor ohms.
Make sure you get one rated for high enough wattage.
Then you could return the black wire to a ground, and the sensor would work again. It's just using a fixed resistor in place of the variable one (rheostat).

[Len]

They look really nice but I just don't think I have a need for the variable control. I have a custom power 'fan bus' I made which depending on which way I plug the fan wires in I can run each fan at either 5v, 7v or 12v. After many months of trial and error I have found that simply running all my fans at 7v is the best compromise between noise and cooling.

I suppose if I decide I can't live without the CPU fan RPM reading I could wire a single rheostat (or maybe only a resistor is needed?) to the CPU fan.

[Len]

Originally posted by plague
well what if you just ran a wire from the ground pin on the mobo header to the ground wire on the molex? Then the rpm monitor would be grounded, and the fan would still be using 7V.

edit: why would you only want 7V for the glaciator fan?? It's weak enough as it is, and not very loud at all.

I could give that a try. Seems simple enough.

The Glaciator fan may be considered quiet in today's market of noisy fans but with my other 7 x 80mm case fans running at 7v the Glaciator stood out as the loudest fan in my system. I dislike noisy PCs and I'm constantly trying to make mine as quiet as possible. So far I've been successful while still maintaining modest overclocks of my CPU and Geforce2 Ultra.

This is probably against the overclocker's oath :) but I actually reduced my CPU overclock from 1405 to 1350 so I could reduce the CPU voltage from 1.95v to 1.85v so that I could tolerate the 4-5C increase in CPU load temps resulting from turning the Glaciator fan down to 7v.

[plague]

Originally posted by Len
This is probably against the overclocker's oath :) but I actually reduced my CPU overclock from 1405 to 1350 so I could reduce the CPU voltage from 1.95v to 1.85v so that I could tolerate the 4-5C increase in CPU load temps resulting from turning the Glaciator fan down to 7v.
::shakes head dissappointedly:: just get bigger speakers:D

[It_The_Cow]

I think that the fan can't sense such low revolutions. Some fans don't register when run at 7v, maybe yours is one of them

[Wa11y]

Originally posted by Diggrr
The RPM sensor needs the black wire to ground. With the 7 volt mod, it's +5.
You should try using a rheostat on 12 volts to get the sensor working, and the fan slowed down.

I would disagree. My MCX462A Swiftech runs off a 4-pin molex connector, and has a three pin connector attached with just a blue wire for the tach. The red and black both go to the Molex.

[Diggrr]

Nope. I said it right. The 7 volt mod is done by taking the black ground wire of a 12 volt fan and attaching it to the positive 5 volt (red) wire. It runs without a ground.
The Swifty does work fine, until you switch wires from ground to + 5 volts.
No ground, no rpm sensing.

There's no such thing as -5 volt or -12 volt in a molex connector. They go to the same place in the power supply. It's just a ground.

[Sonny]

Whoops:D My mistake:o

[Diggrr]

Denada

What I don't understand, is why a molex has seperate wiring all the way back to the psu for the black wires, just to join them on the same solder pad...strange.