Need an electricians's assistance. DELL Fans.

[Princemercury]

This will probably be a simple question to answer for someone...

Some background information:

We have a slew of DELL servers and our company has decided to implement a large scale water cooling solution for our data centers. As many of you know DELL has 3, 4 and 5 pin fan connectors built on their serverboards/motherboards and when a fan is disconnected from one of them you receive the annoying

Alert! Fan failure.
Press F1 to Retry / Continue, F2 to Run setup util...

You can not disable fan check in the System Setup on a DELL machine. So what I'm looking for is what do I need to not "short", eg with a resistor or a capacitor, but connect between the +5v and GND pins to dissipate the 5v of energy and make the system "think" there's a fan there.

Thanks.

+ Something cost effective that we can replicate thousands of times... And we can't use the pins on board to power the individual pumps because the male molex(s) are soldered on and don't provide enough power input.


Edit:
We have a meeting with an electrician today and I have this question posted on several other forums, I'll post the solution we implement if anyone is interested in the future.

 

[masterorion]

have you tried to set the "report keyboard errors" off, if it has that option in the bios? sounds awkward, but ive seen that work before
id have to see the bios. i know on some of the bios's you can set the cpu fan failure detection off. but, that may not be the case with what you are working with

 

[Guppy]

I'm not sure that the fan sensors simply measure resistive load across the power connector. The alarm may actually be triggered off the RPM measurement, in which case a simple solution like you posted would not work. Instead, you'd need a much more sophisticated solution that could spoof the signal on the RPM data wire (could probably be built with a 555 timer or such, but more troublesome than what you're looking for I think).

Or, get the BIOS to ignore it somehow, like Masterorion mentions. Anyway, seeing as how your post was a while ago, I'm curious how you resolved the matter.

 

[Divinius]

Guppy is correct, generally, the motherboard gets tach info back from the sense line of the fan to determine if it's spinning, and how fast. It doesn't monitor the load on the power pins.

The best solution would be to disable the monitoring in the bios. It should be an option in there somewhere.

If you really can't disable it, then you would actually need to "fake" a tach signal to send back to the mobo, which would not be terribly had to do, but would involve more than a simple resistor.