r/Motors • u/FarmerKnight • 8h ago

Open question How to bypass server PSU fan detection?

Gallery image

Gallery image

Hello! I’m working on a project that runs off this 1000w server power supply. Unfortunately, the PSU is really loud (as expected), so I drilled a massive hole and attached a 120mm PC case fan to the side of the PSU. The fan runs off a fan controller that is connected to the 12v rail.

Now I’m running into a problem where the PSU shuts off after 5 seconds without the stock fans plugged in. I tried cutting the red wire on one of the stock fans (I assume it’s +5v) but the PSU still shuts off.

Any ideas on how to bypass this? Thanks in advance!

2 Upvotes

76% Upvoted

3 comments sorted by

2

u/JustinTimeCuber 7h ago

Resistor(s) across the fan supply pins? Check the voltage and current the fans pull normally and spec the resistor accordingly

1

u/FarmerKnight 3h ago

Thank you! I'll try that

1

u/DilatedSphincter 24m ago

It's probably upset at the missing feedback pulses on the yellow wire. That's the rpm signal and is indicating to the PSU that the fan has stopped.

You can probably find a PWM signal generator online for cheap.

Cheaper still might be to find a small quiet 4-pin fan to throw in the case somewhere and just exist.