Run 12v case fan @ 7v ?

[imported_fatal]

Is there an easy way to run case fan @ 7v by switching wires? I want fan to run slower. Can this be done on 3 wire connector or do I need to use 4pin?How do I do this 😕

Thanks

 

[peleejosh]

Best way is to use a fan controller. You can mod a 4 pin molex to run it at 7 volts, but there are some issues with the -5v line. Here is a link.
http://www.bleedinedge.com/guides/7volt_mod/7volt_fan_mod.html

 

[imported_fatal]

Thanks 🙂

 

[Zepper]

Better to use a $2. rheostat from Radio Schlock than mess with that rewiring.

.bh.

 

[Operandi]

SpeedFan?

 

[Goi]

You'll need to calculate the resistance of the trimpot/rheostat/pot needed based on the fan though. Different fans present different loads which require different resistances for the voltage division to work within the desired range. Of course you could get one with a huge resistance but you'll be reducing the precision of your control

 

[lenjack]

peelejosh...I don't see where the -5v line is a factor. the 7 volt trick only uses the 12 and the plus 5.

 

[Zepper]

The 25 ohm, 3 Watt rheostat at RS will work fine in series with most fans. You'd have to have a pretty powerful fan to need something more.

.bh.

 

[kyparrish]

Originally posted by: lenjack
peelejosh...I don't see where the -5v line is a factor. the 7 volt trick only uses the 12 and the plus 5.

I think it has to do with the possibility of some of the power being "sent back" to the PSU, which wouldn't be good.

Earlier today, I did the 5v mod for my panaflo that's on my xp-90, and it's SILENT, but still cooling very well. Looks like the 5v trick isn't risky because you are still using a true ground (5v power and ground for ground), where with the 7v trick you are using the 5v as a ground (12v for power, and 5v for ground).