DDC pumps won't change from 3300RPM

[ozfoggy]

Question for the group. I have a pair of Bykski DDC pumps (B-PMD3-COV) running together under an Alphacool top. MSI Godlike MB. Each one hooked up to 4 pin Molex and each one to a separate 3 pin MB fan header. BIOS set to DC. No matter what I do to voltage settings in BIOS (or Dragon Center), both pumps just run at 3268 - 3300 RPM. Even if I disconnect the fan headers, and just have power (Molex) there is no discernible RPM difference (should be 100%). Stated max RPM is 5000RPM, so I believe I should be able to get at least 4000-4500. Single pump on single molex from PSU behaves the same way.

 

[Zerileous]

Are they PWM pumps? With the BIOS set to DC, it will attempt to vary RPM by changing the voltage to the pumps, however the pumps are not getting voltage from the board rather from the molex, so it has no effect. You should use the BIOS set to PWM or allow the motherboard to provide the current to the pumps providing the headers are adequately rated to do so.

 

[bigtallanddopey]

You cannot just put them into any fan header on the motherboard either. They must be connected to specific ones for pumps, if your board ha them.