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Solved: Computer boots fine when case is open, but won't boot when case is closed.

5K views 13 replies 7 participants last post by  win2kpro 
#1 ·
I have a Dell Optiplex GX270. When I press the power button, the power button light turns amber, I hear some fans spinning, and the CD drive spinning. However, it never gets to the boot screen (or any screen). If I open the case and press the power button, however, the power button turns green and the computer works fine (loads all the way up and functions like normal). If I close the case after it has started, it continues to run fine. I'm guessing / hoping it's not the mother board or power supply that has directly gone bad... but maybe there is a connection or something? that changes from when it's closed to when it's open. I've heard of something like... the motherboard is shorting out by touching the case... but I'm not really sure where to look for that / how. Any suggestions would be appreciated! Thanks!
 
#2 ·
Do you have any amount of dust on the inside of your case? Try vacuuming it out, or better yet using an air duster or air compressor. Dust can cause the strangest of problems. Make sure to get everywhere inside, including all of the vents on the sides, front and back of the case, and the power supply.
 
#3 ·
hi have you rechecked your wiring for damage.also hulkinator has a good point in making sure your clear of dust and debrie however do not on any account use a vaccum in your comp it creates static which is the enemy of mobos and cpu's ie 3volts is enough to kill a chip and static is in the thousands
 
#6 ·
Hi, thanks everyone for the suggestions. I tried to post back earlier, but for some reason the forum wouldn't let me. After hitting "Submit Reply" it would just go to a blank page. Not sure what that was about. So, in the meantime, I decided to take everything completely apart. I just got it put back together and it seems to be working now. There wasn't too much dust and the cords didn't appear damaged. However, I did find a large piece of fuzz hidden between the plastic and power button area... which was the very last thing I disassembled. I'm not 100% sure that was the problem. And I'm not 100% sure the issue is fixed because I previously was able to occasionally get the computer to work with the case closed. If it stays working all of tomorrow, I'll assume it was either the dust or else a fickle connection somewhere. Thanks again for everyone's input!
 
#7 ·
Nope, it didn't stay fixed even though I removed / replaced every single component from the case. The strange thing is that it'll stay working for a little while after I open and close the case. If I come back in an hour or so, it won't boot, however. The fans spin, but the light remains amber and the monitor never wakes up.
 
#8 ·
hi well other than a short which you have looked for it then goes to looking at the psu as a possible but iam not convinced that it is not some sort of short that is not to say you did not do a good job but from your description it seems the logical fault
 
#10 ·
It really sounds like a defective chassis intrusion switch. I would physically remove it and also disable its function in BIOS.

Instructions are here;

http://support.dell.com/support/edocs/systems/opgx270/SM/EN/chsintr.htm

If that doesn't solve the problem, try loosening all the screws that secure the motherboard to the chassis, then screw them back down just "snug" but not too tight and see if the problem continues.
 
#11 ·
Alrighty, that intrusion switch is outta there! The fact that the computer boots fine after opening the case sure makes this tricky/ time-consuming to nail down. Yes, it does also seem like some sort of short somewhere. Seems odd that the short would only affect it while booting. Maybe that's not strange. Otherwise, once it's booted, it'll stay running indefinately.

I appreciate everyone's input so far!
 
#13 ·
It's been a couple of days and all seems to be well! Thanks all! I've learned something from each person's post. Special thanks to win2kpro, replay, and TRS-80 vet who all pointed to the intrusion switch. I guess I was a little slow to believe it as I had at one point tried unplugging the switch with the same intermittent results. I had not, however, disabled it in the BIOS. So, hopefully this is it. Thanks again.
 
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