How to connect multiple fans on one channel AND display correct RPM?

Mayh3M · 11 Dec 2014 at 13:25

Hi.

I bought a Lamptron FC5v2 fan controller and hooked up 3 fans on 2 of the channels each using BitFenix Alchemy 3-Pin to 3x 3-Pin adapters. Everything is functioning properly except the RPM readouts which hover around 300-500 regardless of how fast the fans are spinning.

I read up on this and found that I need to cut the sensor wire (yellow) on 2 out of 3 fans so that the controller doesn't receive mixed signals.

I wanted to know the best way to go about this. Should I cut the wire on the fan ends? or the 3-pin to 3x 3-pin adapter? How should I cut through the sleeves covering the wire? Should I tape each end of the cut wire after doing so? etc. etc.

nutsnut · 11 Dec 2014 at 13:34

I would cut the yellow cable on the 3 x 3pin connector, as these are cheaper than the cost of three replacement fans if you balls it up.

doyll · 11 Dec 2014 at 13:53

It's not hard to just remove the RPM lead from the fan plug.

On one side of fan plug there are 3 holes/slots. If you look into them you will see a metal tab. Push down on that with something like the end of a paper clip so it is below the level of the plastic and pull the lead out of plug. Wrap it with some tape so it can't short out anything and job done.

Late on if you want to use fan with RPM lead, just plug it back into connector.

Mayh3M · 11 Dec 2014 at 14:51

You mean these metal pins?

doyll · 11 Dec 2014 at 15:03

Yes, those are the ones. Push down on those closest to where the wire enters, then pull on the wire and it should slide out of connector.

Mayh3M · 11 Dec 2014 at 15:15

All right thanks.

Mayh3M · 11 Dec 2014 at 17:07

Just to follow up on this, how do I tell which wire lead is the RPM one on an all black fan cable? Am I forced to cut to find out?

doyll · 11 Dec 2014 at 17:20

Mayh3M said:
Just to follow up on this, how do I tell which wire lead is the RPM one on an all black fan cable? Am I forced to cut to find out?

Well, you have to be able to pull one lead out of the three out of connector. Here is a drawing with the pin-out for 3-pin fans. Middle is power so if you pull the wrong one the worst case is fan won't run. :eek:

If you pull the wrong one, plug it back in and put the one on other side of plug.

Mayh3M · 11 Dec 2014 at 17:37

Ah the fact that the two opposite sides aren't identical mean you should definitely be able to know which wire is which even without coloured wires. That's what I was looking for. Thanks.

Mayh3M · 11 Dec 2014 at 18:58

Is masking tape or sellotape suitable for taping the exposed wire once I take it out?

doyll · 11 Dec 2014 at 19:18

They will work, but will be very hard to remove later. Could use a piece of medical tape, tape, from a plaster, etc. All the tape is for is so it cannot touch anything electrical and short to something else. The lead has no power in itself to worry about.

Slip the tip under the braided cover you have on your leads.

Tealc · 11 Dec 2014 at 20:16

You'd have thought Bitfenix would have designed their leads in such a way that only one of the attached fans gives a readout. The tach circuit on the motherboard must be well confused by three fan signals overlapping.

Mayh3M · 11 Dec 2014 at 20:31

Worked like a charm. I'm glad I didn't have to cut anything and can easily undo everything I did if need be. Thanks for the help doyll. Much appreciated.