MDD fans at full throttle unless ADC monitor is used

[Isaac_Coker]

I know these are known for being loud but I’m not sure if this is a known trait of the MDD PowerMacs. The moment I disconnect the adc monitor, the fans speed up and stay at full speed. I can use two monitors no issue but as soon as the adc monitor isn’t connected the fans speed up. The fans slow back down to normal when it’s reconnected. Is this normal or is something failing?

 

[AlixSPQR]

Have you tried to reset PMU and NVRAM?

 

[Hrududu]

Thats an odd one. Mine ramp up the fans when they go to sleep. They're just notorious for bad power supplies though, and I know both of mine are flaky. My dual 1,42 will ONLY power on using the button on a 17 ADC monitor (not a 22, 20, or 23 though) so something about the power draw from the display certainly has an effect on them.

 

[SnakeCoils]

On the MDD (both FW400 and FW800) the same behaviour occour on plugging and unplugging a passive firewire HDD drive (typically the portable 2.5" ones), so it seems the MDD power supply works at its best expecially under load. It was a common practice for me to keep permanently a FW drive attached to lowering the PSU fan noise.

 

[for this]

I don't have an ADC monitor to try. But I can imagine that unplugging it while the Mac is turning on can trigger the behavior since it is electrically connected the the video card and draws power directly from it. But if it still happens after restarting or turning off (the Mac) and on again then I have no idea.

 

[Isaac_Coker]

I have reset the pram, but not the pmu. I will definitely try that next, totally forgot about that being an option. It also has the later open firmware that was supposed to improve the noise but I can’t see if it does anything.