Basic Switch

[rbt]

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?.. If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?
Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles



SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

tis

 

[kony]

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

"Usually" fans run from 12V, the (usually) yellow wire on a
PSU lead. The switch would break that, or the ground, not
the red wire to turn the fan(s) off.

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

I presume by "15a" and "3a" you actually mean "0.15A" and
"0.3A", since there is no practical fan that would be put in
a PC that uses 3A or more current.

We could do the math to determine the total current of these
three fans but we dont' really need to, it's certainly still
far below what a 3A/20A switch can handle.

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?..

Yellow is 12V, red is 5V.

If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Well then how did you want to do it? It's not a problem
handling the tiny bit of current three fans use. Relatively
there are devices that use far less, but in the context of
computer equipment, 3 fans is nothing, you would be hard
pressed to find a switch large enough that it can be
reasonably switched and have it unable to handle (additively
as listed above for the three fans) 630mA.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?

No need for a relay, it'd just be an unnecessary expense,
unnecessary slight increase in complexity and a mechanical
part that slightly increases chances of failure as well as
taking up more space.

Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles

I highly doubt it has a relay built in. More likely it's a
SPDT switch, meaning it has one contact (call it contact #2)
that's open to contact #1 when in one position, and closed
to #3 in that position. Flip the switch and then #2 is
closed to #1 and open to #3. That'll work fine, you'd just
ignore position #1 or #3, and wire the power and fan leads
to the other two remaining positions.

SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

What you propose to do will work. There are several ways to
do it so if you're ok with having to switch them on and off,
that's fine. If you only have these 3 fans in addition to
the one in your PSU, personally I'd consider leaving the
slowest of the 3 (probably the 0.13A fan) running even when
the system is idle, and having that one mounted in the back
wall of the case as an exhaust. While the CPU (and perhaps
video card, if you're a gamer) will significantly decrease
power consumption when idle, it's still better to have more
than just the PSU as an exhaust, especially since it would
mean the PSU was then drawing all the heated air up into
itself which can contribute to shorter lifespan.

 

[rbt]

HUGE Thanks for your reply,

yur right - it was a 0.15a. The 0. was miles off to the left of the 15

on the ttl amps, the maths is ok yep - when i was reading it as 15 amps
I was worried, electricity really worries me, even 12volts.

OMG, red and yellow corrected...

and Ive just noticed the switch has two "on" stamped into it, not a
"on" or "off". This must tie up with the two amps mentioned

Hey man, your good, I did buy a 3A/20A SPDT & I found another fan. That
makes 7 all up, the bluddy thing should be catching a cold.

There is two in the 430w Thermatek PSU & one on the CPU to the mobo, am
leaving those 3 alone, the ps had no fan sensor wire, the CPU fan is
quiet when is cool and is very responsive to easytune5. No
top-blow-hole in the case, thinking of cutting one in, does get very
warm on the top panel of the case. The rear exhaust from the PSU seems
weak and doesnt get out a very warm airflow.

Will put TWO fans to rear exhaust, one fan to switch position 1 of my
new SDDT switch and the other, plus the remaining fans, put to switch
position 2, which is the 20amp channel if Im getting it right.... that
will satisfy my paranoria & give me a constant "on" state of fan/s.

I am going to take a uneducated guess and pick the middle post of the
switch as the ground

Last week I had this rig in a AT Tower Case, then a fancy side-window
top-holed full-height ATX and now this ATX midi. There wasnt been a
marked temp diff in any unless care taken with cable/wire/ribbon
routing and even that only saved 8degrees - prolly back to what it
should be.

How's this for food for thought - an CPU/GPU water-cooler would cost
more than half as a airconditioner, and then we'd both be
cool...OMG..lol..

many tx again

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

"Usually" fans run from 12V, the (usually) yellow wire on a
PSU lead. The switch would break that, or the ground, not
the red wire to turn the fan(s) off.

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

I presume by "15a" and "3a" you actually mean "0.15A" and
"0.3A", since there is no practical fan that would be put in
a PC that uses 3A or more current.

We could do the math to determine the total current of these
three fans but we dont' really need to, it's certainly still
far below what a 3A/20A switch can handle.

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?..

Yellow is 12V, red is 5V.

If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Well then how did you want to do it? It's not a problem
handling the tiny bit of current three fans use. Relatively
there are devices that use far less, but in the context of
computer equipment, 3 fans is nothing, you would be hard
pressed to find a switch large enough that it can be
reasonably switched and have it unable to handle (additively
as listed above for the three fans) 630mA.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?

No need for a relay, it'd just be an unnecessary expense,
unnecessary slight increase in complexity and a mechanical
part that slightly increases chances of failure as well as
taking up more space.

Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles

I highly doubt it has a relay built in. More likely it's a
SPDT switch, meaning it has one contact (call it contact #2)
that's open to contact #1 when in one position, and closed
to #3 in that position. Flip the switch and then #2 is
closed to #1 and open to #3. That'll work fine, you'd just
ignore position #1 or #3, and wire the power and fan leads
to the other two remaining positions.

SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

What you propose to do will work. There are several ways to
do it so if you're ok with having to switch them on and off,
that's fine. If you only have these 3 fans in addition to
the one in your PSU, personally I'd consider leaving the
slowest of the 3 (probably the 0.13A fan) running even when
the system is idle, and having that one mounted in the back
wall of the case as an exhaust. While the CPU (and perhaps
video card, if you're a gamer) will significantly decrease
power consumption when idle, it's still better to have more
than just the PSU as an exhaust, especially since it would
mean the PSU was then drawing all the heated air up into
itself which can contribute to shorter lifespan.

 

[rbt]

The switch would break that, or the ground, not
the red wire to turn the fan(s) off.

is the opposite tru in all states...

The switch would make that, or the power, not
the black(ground) wire to turn the fan(s) on

no wonder im frightened of it... that how ive been seeing it

HUGE Thanks for your reply,

yur right - it was a 0.15a. The 0. was miles off to the left of the 15

on the ttl amps, the maths is ok yep - when i was reading it as 15 amps
I was worried, electricity really worries me, even 12volts.

OMG, red and yellow corrected...

and Ive just noticed the switch has two "on" stamped into it, not a
"on" or "off". This must tie up with the two amps mentioned

Hey man, your good, I did buy a 3A/20A SPDT & I found another fan. That
makes 7 all up, the bluddy thing should be catching a cold.

There is two in the 430w Thermatek PSU & one on the CPU to the mobo, am
leaving those 3 alone, the ps had no fan sensor wire, the CPU fan is
quiet when is cool and is very responsive to easytune5. No
top-blow-hole in the case, thinking of cutting one in, does get very
warm on the top panel of the case. The rear exhaust from the PSU seems
weak and doesnt get out a very warm airflow.

Will put TWO fans to rear exhaust, one fan to switch position 1 of my
new SDDT switch and the other, plus the remaining fans, put to switch
position 2, which is the 20amp channel if Im getting it right.... that
will satisfy my paranoria & give me a constant "on" state of fan/s.

I am going to take a uneducated guess and pick the middle post of the
switch as the ground

Last week I had this rig in a AT Tower Case, then a fancy side-window
top-holed full-height ATX and now this ATX midi. There wasnt been a
marked temp diff in any unless care taken with cable/wire/ribbon
routing and even that only saved 8degrees - prolly back to what it
should be.

How's this for food for thought - an CPU/GPU water-cooler would cost
more than half as a airconditioner, and then we'd both be
cool...OMG..lol..

many tx again

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

"Usually" fans run from 12V, the (usually) yellow wire on a
PSU lead. The switch would break that, or the ground, not
the red wire to turn the fan(s) off.

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

I presume by "15a" and "3a" you actually mean "0.15A" and
"0.3A", since there is no practical fan that would be put in
a PC that uses 3A or more current.

We could do the math to determine the total current of these
three fans but we dont' really need to, it's certainly still
far below what a 3A/20A switch can handle.

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?..

Yellow is 12V, red is 5V.

If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Well then how did you want to do it? It's not a problem
handling the tiny bit of current three fans use. Relatively
there are devices that use far less, but in the context of
computer equipment, 3 fans is nothing, you would be hard
pressed to find a switch large enough that it can be
reasonably switched and have it unable to handle (additively
as listed above for the three fans) 630mA.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?

No need for a relay, it'd just be an unnecessary expense,
unnecessary slight increase in complexity and a mechanical
part that slightly increases chances of failure as well as
taking up more space.

Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles

I highly doubt it has a relay built in. More likely it's a
SPDT switch, meaning it has one contact (call it contact #2)
that's open to contact #1 when in one position, and closed
to #3 in that position. Flip the switch and then #2 is
closed to #1 and open to #3. That'll work fine, you'd just
ignore position #1 or #3, and wire the power and fan leads
to the other two remaining positions.

SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

What you propose to do will work. There are several ways to
do it so if you're ok with having to switch them on and off,
that's fine. If you only have these 3 fans in addition to
the one in your PSU, personally I'd consider leaving the
slowest of the 3 (probably the 0.13A fan) running even when
the system is idle, and having that one mounted in the back
wall of the case as an exhaust. While the CPU (and perhaps
video card, if you're a gamer) will significantly decrease
power consumption when idle, it's still better to have more
than just the PSU as an exhaust, especially since it would
mean the PSU was then drawing all the heated air up into
itself which can contribute to shorter lifespan.

 

[Paul]

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?.. If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?
Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles



SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

tis

In terms of control, you should aim for a simple setup. You should have
the "base" set of fans that are always running. You don't need any
switch in that path. You can use a switch to activate your "extra"
fans.

(Not that I approve of this plan, as the best way to do it is just
set the fans up to handle the situation no matter what, as if a friend
operates your machine, they might forget to flip the switch when needed.
One poster here, had a switch for his water cooling system,
his girl friend used his computer, and forgot to switch on the
water system. Fried CPU according to him.)

First of all, be careful with the wire color, because the color standard
for disk drive connectors is different than the one for three wire
fans. So you cannot just wire "yellow to yellow", as that would be
incorrect. You can find connector pinout information, to verify what
you are about to do, so don't trust my figures below, but check
them yourself to be sure.

One way to figure out the wiring on the fan, is open your motherboard
manual. The manual will label the three fan pins, which are "RPM", "+12V",
and "Ground". The center pin (red wire) on a three pin fan header
is +12V. The black wire is ground (so at least that color is consistent).
The remaining yellow wire is the RPM signal. Fans come either with three
wires or with two wires, and a two wire fan is missing the yellow RPM signal.
A two wire fan has a red and a black wire, and red is +12V and black is
GND.

You don't need the RPM signal, and in this case, I don't see any benefit
from hooking it up.

The messy part of the job, is the connectors that are on everything.
If the fans in question, had disk drive power connectors on the end,
there would be less work to do. If the fans had the small three pin
connectors on the end, you might consider picking up some Molex
4 pin disk drive to 3 pin fan adapter cables, as a quick and easy
way of getting the wiring right.

With the fan I have sitting in front of me, this is the wiring
color scheme for the three pin small connector (the connector that
would normally go to the motherboard fan header). This is the view
looking into the end of the fan cable's three pin connector. Notice
that the pin holes are close to the place where the orienting tab
fits, when the fan connector is plugged into the motherboard.

Fan cable 3 pin connector Molex Drive Connector

+------------------------+ +12V GND GND +5V
| | Yellow Black Black Red
| Yellow Red Black | X X X X
| RPM +12V GND |
| x x x |
| ____________________ |
|_| |_|

To run the fans, all you need is to break the yellow wire on
the Molex disk drive extender cable, with your switch. Once you
modify the Molex extender cable, it should only be used for
your fan system, as switching the power off to a disk drive
would not be a smart thing to do. You cut the Yellow wire
on the Molex drive extender assembly (near the source end),
so that the switch can open or close the Yellow +12V path.

/
/
Yellow <---------* *-------->
Black <---------------------->
Black <---------------------->
Red <---------------------->

If you don't plan on getting Molex drive to three pin adapters
or the like, then the wiring straight from a Molex drive cable
to the fans would look like this. The Fan_Yellow is optional
and a computer case fan likely doesn't have an RPM. You don't have
to wire the RPM signal to anything. Make sure you insulate the end
of the Fan_Yellow wire, so it doesn't contact anything. The "X"
here means "No Connection" and "tape off the end".

/
/ X----------- Fan_Yellow (RPM)
Yellow <---------* *--------> >----------- Fan_Red (+12V)
Black <----------------------> >----------- Fan_Black (GND)
Black <---------------------->
Red <---------------------->

With more than one fan to be controlled by the switch, all the
fans run in parallel. In other words, all the Fan black wires are
joined together. All the Fan red wires are joined together. Then
connect the clump of Fan_Red wires as in the above diagram. Connect
the clump of Fan_Black wires as above.

If you have a three position rocker switch, the positions would
be ON-OFF-ON. There are a million different kinds of switches,
and it is pretty hard to guess at what you've got. If the
switch has a center row/pins and two end rows/pins, then
the switch would look like this, logically speaking. You use
a center pin, and one end pin, to get the switching action.

Rocker switch, three position Wiper closes, center to one end.

/
|\_____/| /
|_______| ON * * * ON
* * *

To use the rocker, you can use a center pin (common) and one
end pin, like this. This is what it would look like, if I
was interrupting the flow of current in the Yellow Molex wire.

/
/
ON * * * ON
| |
| |
Yellow >-----+ +----> Yellow

If you are still unsure about what you are doing, remember
that the computer works best with good cooling, and you
can always select just enough fans to keep the computer
cool at all times, and leave it that way. I don't modify
my fan cooling, and all my fans run at a fixed speed.
That way, there is no annoying ramping up and down of
fans. The computer I'm typing this on is rather loud,
but I assure you, it is always cool And yes, I could
make a very complicated technical scheme to control the
fans, but I don't do it.

You can buy fan controllers that fit in disk drive or
floppy bays. This one, for example, takes fans from
all the way off to all the way on. Some controllers
don't have an off position. The lamps that come with
this kit are overkill. While there are many different
brands and models of these things, quite a few of
them are flaky. But there is less stripping of
wires and soldering, using a controller.

VANTEC NXP-305-SL Fan & Light Controller Panel, Silver - Retail
http://www.newegg.com/Product/CustratingReview.asp?Item=N82E16813999903

This is the controller part. Three fan control channels. One
for lights.

http://images10.newegg.com/NeweggImage/productimage/13-999-903-01.JPG

The CCFL lamps that come with this kit are overkill.

http://images10.newegg.com/NeweggImage/productimage/13-999-903-03.JPG

Paul

 

[kony]

The switch would break that, or the ground, not
the red wire to turn the fan(s) off.

is the opposite tru in all states...

The switch would make that, or the power, not
the black(ground) wire to turn the fan(s) on

no wonder im frightened of it... that how ive been seeing it

You'd want the 12V, power lead from the PSU wired to the
middle switch contact (let's call that contact #2).

Wire the fans' positive power leads to switch contact #1 (or
contact #3, pick one or other other and wire them all up to
the same contact).

Wire all the fans' negative, grounds to the black PSU Gnd
wire, they are not switched.

You "could" do it the opposite, switching the ground instead
of the power but there is no reason to do it in your
situation.

 

[rbt]

I must be dixlestic

power supply wire to the center post
power device wires to side post
ground to ground wires

ok, i can see a circut there...
& i need to ask if this is ok

I have a molex extension & and molex extension wih 3 extra molex plugs
I would like to put the switch into the extension which will hopefully
turn off everything forwad of it

snip the 12v about halfway along the molex extension
wire one end of the cut, the 12V power lead from the PSU to the middle
switch contact #2
Wire the other end of the cut to switch contact #1
Wire all the fans' negative grounds to the black PSU Gnd

Does this achieve the same thing or am I going to be turning off that
whole rail or even blowing it up. I am thinking my advantage is I dont
have to put connectors on half of the wires - yerrr, id rather write
emails...lol..

huge thanks again - you have made it very clear, sorry to muddy it with
the last

 

[rbt]

I must be dixlestic

power supply wire to the center post
power device wires to side post
ground to ground wires

ok, i can see a circut there...
& i need to ask if this is ok

I have a molex extension & and molex extension wih 3 extra molex plugs
I would like to put the switch into the extension which will hopefully
turn off everything forwad of it

snip the 12v about halfway along the molex extension
wire one end of the cut, the 12V power lead from the PSU to the middle
switch contact #2
Wire the other end of the cut to switch contact #1
Wire all the fans' negative grounds to the black PSU Gnd

Does this achieve the same thing or am I going to be turning off that
whole rail or even blowing it up. I am thinking my advantage is I dont
have to put connectors on half of the wires - yerrr, id rather write
emails...lol..

huge thanks again - you have made it very clear, sorry to muddy it with
the last

 

[kony]

I must be dixlestic

power supply wire to the center post
power device wires to side post
ground to ground wires

ok, i can see a circut there...
& i need to ask if this is ok

I have a molex extension & and molex extension wih 3 extra molex plugs
I would like to put the switch into the extension which will hopefully
turn off everything forwad of it

yes that'll work

snip the 12v about halfway along the molex extension

I'd think you need to snip all three 12V leads, since they
usually have 3 wires, one per each socket going to the one
plug.

wire one end of the cut, the 12V power lead from the PSU to the middle
switch contact #2
Wire the other end of the cut to switch contact #1
Wire all the fans' negative grounds to the black PSU Gnd
yes


Does this achieve the same thing or am I going to be turning off that
whole rail or even blowing it up.

No, it will only turn off anything downstream of the switch
on that set of wires.

I am thinking my advantage is I dont
have to put connectors on half of the wires - yerrr, id rather write
emails...lol..

True, so long as all your fans already had connectors to
mate with your splitter/extension cable.

 

[rbt]

Many thanks for all who assited -

End result temps

normal use - CPU 30 GPU 41
gaming use - CPU 41 GPU 78
with fans gaming - CPU 31 GPU 43

A great result - many thanks again

 

[rbt]

ta for that, these are the go...

I am tryiing to wire up three fans.
I have a PS cable-adapter that has one male and 3 three female PS
plugs.
I would like to put in a switch.
I have another male-female PS cable bridge and a 3 pole on-off switch.
I dont think I should simply break the red with the switch

Will three 12v .18a, 12v 15a &12v 3a fans burn out the switch even if
it is stamped with [3amp 250vac] & [20amp 125 vac]?

In a PS cable-loom, is the Red cable 12volts and the Yellow cable 5
volts?.. If so I could split the fans accros the PS positives but I
still dont like the idea of the swict being wired directly into the
power loom.

Can I fit a relay? or am i worring about nothing - it would seems a
relay-switch would be safer?
Or, with the right wiring is the swith I bought already a built-in
relay switch? - it has three poles



SOME BACKGROUND

I use my machine in two modes, flat-out and idle, so Iv decided to load
it up with fans and a on-off switch running off the standard power
leads.

Ive spent some time with easy-tune5, speedfan, the 4 fan connectors on
my Gigabyte GAK8N-SLi & 4 odd-bod collection of cpu & ps fans.

Ive been trying to rig them all to go quiet but cant afford a proper
fans & solution - so just on and off would be nice.

tis

In terms of control, you should aim for a simple setup. You should have
the "base" set of fans that are always running. You don't need any
switch in that path. You can use a switch to activate your "extra"
fans.

(Not that I approve of this plan, as the best way to do it is just
set the fans up to handle the situation no matter what, as if a friend
operates your machine, they might forget to flip the switch when needed.
One poster here, had a switch for his water cooling system,
his girl friend used his computer, and forgot to switch on the
water system. Fried CPU according to him.)

First of all, be careful with the wire color, because the color standard
for disk drive connectors is different than the one for three wire
fans. So you cannot just wire "yellow to yellow", as that would be
incorrect. You can find connector pinout information, to verify what
you are about to do, so don't trust my figures below, but check
them yourself to be sure.

One way to figure out the wiring on the fan, is open your motherboard
manual. The manual will label the three fan pins, which are "RPM", "+12V",
and "Ground". The center pin (red wire) on a three pin fan header
is +12V. The black wire is ground (so at least that color is consistent).
The remaining yellow wire is the RPM signal. Fans come either with three
wires or with two wires, and a two wire fan is missing the yellow RPM signal.
A two wire fan has a red and a black wire, and red is +12V and black is
GND.

You don't need the RPM signal, and in this case, I don't see any benefit
from hooking it up.

The messy part of the job, is the connectors that are on everything.
If the fans in question, had disk drive power connectors on the end,
there would be less work to do. If the fans had the small three pin
connectors on the end, you might consider picking up some Molex
4 pin disk drive to 3 pin fan adapter cables, as a quick and easy
way of getting the wiring right.

With the fan I have sitting in front of me, this is the wiring
color scheme for the three pin small connector (the connector that
would normally go to the motherboard fan header). This is the view
looking into the end of the fan cable's three pin connector. Notice
that the pin holes are close to the place where the orienting tab
fits, when the fan connector is plugged into the motherboard.

Fan cable 3 pin connector Molex Drive Connector

+------------------------+ +12V GND GND +5V
| | Yellow Black Black Red
| Yellow Red Black | X X X X
| RPM +12V GND |
| x x x |
| ____________________ |
|_| |_|

To run the fans, all you need is to break the yellow wire on
the Molex disk drive extender cable, with your switch. Once you
modify the Molex extender cable, it should only be used for
your fan system, as switching the power off to a disk drive
would not be a smart thing to do. You cut the Yellow wire
on the Molex drive extender assembly (near the source end),
so that the switch can open or close the Yellow +12V path.

/
/
Yellow <---------* *-------->
Black <---------------------->
Black <---------------------->
Red <---------------------->

If you don't plan on getting Molex drive to three pin adapters
or the like, then the wiring straight from a Molex drive cable
to the fans would look like this. The Fan_Yellow is optional
and a computer case fan likely doesn't have an RPM. You don't have
to wire the RPM signal to anything. Make sure you insulate the end
of the Fan_Yellow wire, so it doesn't contact anything. The "X"
here means "No Connection" and "tape off the end".

/
/ X----------- Fan_Yellow (RPM)
Yellow <---------* *--------> >----------- Fan_Red (+12V)
Black <----------------------> >----------- Fan_Black (GND)
Black <---------------------->
Red <---------------------->

With more than one fan to be controlled by the switch, all the
fans run in parallel. In other words, all the Fan black wires are
joined together. All the Fan red wires are joined together. Then
connect the clump of Fan_Red wires as in the above diagram. Connect
the clump of Fan_Black wires as above.

If you have a three position rocker switch, the positions would
be ON-OFF-ON. There are a million different kinds of switches,
and it is pretty hard to guess at what you've got. If the
switch has a center row/pins and two end rows/pins, then
the switch would look like this, logically speaking. You use
a center pin, and one end pin, to get the switching action.

Rocker switch, three position Wiper closes, center to one end.

/
|\_____/| /
|_______| ON * * * ON
* * *

To use the rocker, you can use a center pin (common) and one
end pin, like this. This is what it would look like, if I
was interrupting the flow of current in the Yellow Molex wire.

/
/
ON * * * ON
| |
| |
Yellow >-----+ +----> Yellow

If you are still unsure about what you are doing, remember
that the computer works best with good cooling, and you
can always select just enough fans to keep the computer
cool at all times, and leave it that way. I don't modify
my fan cooling, and all my fans run at a fixed speed.
That way, there is no annoying ramping up and down of
fans. The computer I'm typing this on is rather loud,
but I assure you, it is always cool And yes, I could
make a very complicated technical scheme to control the
fans, but I don't do it.

You can buy fan controllers that fit in disk drive or
floppy bays. This one, for example, takes fans from
all the way off to all the way on. Some controllers
don't have an off position. The lamps that come with
this kit are overkill. While there are many different
brands and models of these things, quite a few of
them are flaky. But there is less stripping of
wires and soldering, using a controller.

VANTEC NXP-305-SL Fan & Light Controller Panel, Silver - Retail
http://www.newegg.com/Product/CustratingReview.asp?Item=N82E16813999903

This is the controller part. Three fan control channels. One
for lights.

http://images10.newegg.com/NeweggImage/productimage/13-999-903-01.JPG

The CCFL lamps that come with this kit are overkill.

http://images10.newegg.com/NeweggImage/productimage/13-999-903-03.JPG

Paul