why does my Power Mac G5 keeps going into sleepmode???

Hello Gabriel,

Have you blown the dust out lately?

If you can ever...

Get Temperature Monitor to see if it's heat related...

http://www.macupdate.com/info.php/id/12381/temperature-monitor

If you don't know the model, find the Serial# & use it on one of these sites, but don't post the Serial# here...

http://www.chipmunk.nl/klantenservice/applemodel.html

http://www.appleserialnumberinfo.com/Desktop/index.php

How to find the serial number of your Apple hardware product...

http://support.apple.com/kb/HT1349

Have you done a PRAM reset, CMD+Option+p+r...

http://support.apple.com/kb/HT1379

In fact, do 3 in a row, takes a bit of time.

How to reset the SMU/PMU on a Power Mac G5 (Late 2004) or Power Mac G5 (Late 2005) ...

http://support.apple.com/kb/HT1436

Earlier G3, G4, G5 models...

http://support.apple.com/kb/HT1939

So, you can't even do a PRAM reset?

Do you know if Firmware Password is set?

Firmware password protection in Mac OS X ...

http://support.apple.com/kb/HT1352

It would block usage of all the startup keys, like C, N, T, D, CMD+s, CMD+Option+p+r, CMD +v, Option boot will show a lock, and Shift, as well as booting from anything but the Hard Drive.

Force Removing Password Protection

1) Add or remove DIMMs to change the total amount of RAM in the computer.

2) Then, the PRAM must be reset 3 times. (Command + Option + P + R).

http://www.securemac.com/openfirmwarepasswordprotection.php