Mac Pro 3,1 (early 2008) wont turn on unless i unplug/replug AC

[mys7]

Hi everyone! i got a late 2008 Mac Pro 3,1 that still kicks asses (running patched Big Sur and Windows 11). Tbh since i got my M1 air i barely use it but, when i need it, it doesn't always turn on. I have to unplug/replug AC cable and it will work. I already tried to reset SMC without success. Can someone help me? Thank you in advance

 

[glenthompson]

I had the same Mac Pro that wouldn’t turn on unless you tried multiple times. Finally replaced the power supply and that fixed the problem. Your unpluggingnthe PS may be resetting something internally that allows it to power on. When you try to power on, does anything happen? Power LED, fans, etc?

 

[mys7]

I had the same Mac Pro that wouldn’t turn on unless you tried multiple times. Finally replaced the power supply and that fixed the problem. Your unpluggingnthe PS may be resetting something internally that allows it to power on. When you try to power on, does anything happen? Power LED, fans, etc?

When i try to power on nothing happens. Unplugging may reset SMC?

 

[MultiFinder17]

I’m gonna agree with @glenthompson that it’s most likely your power supply slowly pooping out. I’d look for another one, swap it out, and see if that doesn’t fix your problems

 

[mys7]

Thank you for the sad news... i see they're quite expensive

 

[NewbiePPC]

Some months ago I replace my 3,1 power supply with one from a 1,1. No issues until now

 

[Steviewest]

I think a low PRAM battery will cause those symptoms. Presume you've replaced it? It's a CR2032.

 

[mys7]

I think a low PRAM battery will cause those symptoms. Presume you've replaced it? It's a CR2032.

Omg how could I forgot this ? I think you're right I'm going to buy a CR2032 and try ASAP

 

[DCBassman]

Omg how could I forgot this ? I think you're right I'm going to buy a CR2032 and try ASAP

Do let us know if it worked!

 

[mys7]

Hi! i replaced the battery and the problems seems solved, the mac pro turn on and off perfectly. Since i replaced the battery the fun run FULL speed all of the time! ? i'll try a SMC reset, if you have any suggestion...

 

[mys7]

The IO fan goes crazy... i had to keep it quiet with smcFanControl (temperatures are ok anyway)

 

[Steviewest]

Yes, try both SMC and PRAM resets. Now that the battery can keep these in an uncorrupted state, the reset should stick.
(When the battery is low, they keep getting corrupted even after a reset)

 

[Steviewest]

It's also possible that it thinks the case is still open. If resetting doesn't work, open up the case and close it again.