Fans race & screen blanks

[peterc1066]

HP Compaq dc7800 small form factor PC.   runs WIN 7 Home Premium.   Boots normally but after approx 20 minutes both fans race and screen blanks and have to disconnect power. Restarts and recovers to WIn 7 but fault re-occurs continually. Have reseated RAM. Cleaned PSU and fans.  Nothing appears to be overheating. Any help appreciated..

[itsmyname]

@peterc1066 -- after approx 20 minutes both fans race and screen blanks and have to disconnect power. 

I think that your computer has "crashed", and the restart causes the fans to run at 100%.

When your computer successfully restarts,

Acccess "System Properties", and click the "Advanced" tab (left side of the above image).

Further down, in the group below "User Profiles", click on the (unseen in this screen-shot) "Settings" button to see the right-side of the above image. 

Remove the check-mark from "Automatically restart", and click OK.

Tell us what you see (if anything) the next time that the computer crashes.

[peterc1066]

Removed check mark in  "automatically restart"  But it still crashed a couple of times.. As I wanted to watch the screen when it "crashed" I have adjusted the "Power Options"  So that screen never turns off(was 10mins) . That was a 2pm today and still  no "crashing"  Have rebooted several times and still ok!...  .    ??

[itsmyname]

@peterc1066 -- still OK

Is that bad, or is that good?

[peterc1066]

Good and Bad,  now it runs without crashing but when I  shut it down it reboots to start up without me pressing aything - that occurs every time. So have to stop it by pulling power plug

[itsmyname]

@peterc1066  -- have to stop it by pulling power plug

It would be better if when it restarted, you would press a key to enter BIOS SETUP.

Then, at that screen, hold-down the on/off button until the computer powers-off.

If it still restarts, enter BIOS SETUP, to see if the "restart after AC power is restored" is enabled, and needs to be disabled.

[peterc1066]

I can see no mention in BIOS of  "restart after AC power is restored" option.  But I can at screen power off  hold-down on/off button for a few seconds - then computer will stay off until  next  on-press, when fans initially race but slow down and computer boots normally.

[itsmyname]

@peterc1066 -- I can see no mention in BIOS of  "restart after AC power is restored" option.

This option is usually within the "Power" pull-down.  The wording may be different.

[peterc1066]

As computer is usable now I'll leave things as they are.  Thanks for assistance.