Matching Noctua fans to Dell rack switch? (Modding)

[BrinkGG]

So I've got a Dell Powerconnect 2848 that does exactly what I need, but I am bothered by one thing: I replaced the stock delta fans (loud) with Noctua 40x10 12v fans. They work, BUT the switch complains in the console with:

>FAN #1 IN NON-FUNCTIONAL STATE - REPLACE 
>FAN #2 IN NON-FUNCTIONAL STATE - REPLACE 

And the fan light on the front flashes red and green constantly, which again states a failed fan. 

 

It's been running fine and has not gone above operating temp for multiple days at near max load.

 

Here's my plan: Add resistance to the voltage line on the Noctua fan so that the switch thinks it's got the delta fan plugged in and stops complaining. 

 

Thoughts? 

[Bombastinator]

It depends on how the system is detecting the fans in the first place.  Maybe find that out.  Will Dell say?

[Radium_Angel]

22 minutes ago, BrinkGG said:

Here's my plan: Add resistance to the voltage line on the Noctua fan so that the switch thinks it's got the delta fan plugged in and stops complaining. 

That's typically what you have to do, the fans in Dell servers are "intelligent" insofar as they are not standard pinouts and communicate with the BIOS through extra wires or non-standard wiring layout.

Because of this a straight up swap doesn't work (as you have seen)

There are some good tutorials on how to mod new fans to play nice, if you are good with a soldering gun and wiring

[BrinkGG]

53 minutes ago, Radium_Angel said:

That's typically what you have to do, the fans in Dell servers are "intelligent" insofar as they are not standard pinouts and communicate with the BIOS through extra wires or non-standard wiring layout.

Because of this a straight up swap doesn't work (as you have seen)

There are some good tutorials on how to mod new fans to play nice, if you are good with a soldering gun and wiring

Soldering is not an issue. And these fans are just 3 pin DC fans controlled by the input voltage (start at 6.4v, ramps up to 12v when under full load) I honestly don't even think the sense wire is doing anything. I also tried putting noctua's included low noise adapter (resistors on positive) inline, but because the connectors are repinned to match the deltas that were in it (Pin 1 is 12v, Pin 2 is sense, Pin 3 is ground if looking from the flat side going left to right), the resistors are on the sense wire, and are useless. 

 

[BrinkGG]

1 hour ago, Bombastinator said:

It depends on how the system is detecting the fans in the first place.  Maybe find that out.  Will Dell say?

As far as I can find, it's just based off of the resistance from the fans to tell if they have load. 

[Kilrah]

Some of them have an actual controller in the fan, there may be a line that seems like it would be just a sense wire but it's some more complex bidirectional communication.

 

 

Also some have fast fans that run at like 6K RPM at max, during POST the fan is set to full power and if your quiet fan only runs at 3K it'll be considered as a fan failure.

[Bombastinator]

3 hours ago, BrinkGG said:

As far as I can find, it's just based off of the resistance from the fans to tell if they have load. 

It’s unusual for large companies to spend money on things like wire when they don’t do anything.  Not unheard of, but unusual.  Someone mentioned tutorials on how to modify fans to work with this system but left no links.