[Jayce]

I had a problem with this system last week. The fan had a good chunk of dust in it, so I blasted it out. Then I get a call today (a week later) saying that it's happening again. The fan just runs full bore while the system itself never seems to turn on.

Dell 740 Optiplex.

edit - oh wow, I just got it up and running. jdklafjsdl;kfas

2nd time now. Why would this keep happening?

[Mak213]

Sounds like the controller for the fan might be bad. Maybe a replacement is in order. Could be that the fan was caked with dust for so long that the ontroller thinks it needs to run full bore to keep the system cool.

[Jayce]

That's what I thought too, but I used an entire can of air just blasting this computer, and it wasn't even all that bad. It's a relatively new computer, but I think it's JUST out of reach of warranty.

I ended up whipping up an HP desktop for that user, so I can take my time troubleshooting this particular Optiplex... along with the other 30 desktops sitting around I gotta figure out.

[gary0]

We have had this on a previous Optiplex; turn it on and nothing but the fan runs and it runs loud. Other times turn it on and it boots. Eventually it never boots again.
In our case it turned out to be the processor was not making good contact with the socket after a period of time. And it began to happen on all the PCs of that model. The simple crude diagnostic was if it was booting bump the case of the PC slightly does it cause the non booting issue.
Dell replaced several motherboards and processors for us. We took the rest out of service because they were in a mission critical location.

[c0rr0sive]

At our vocational school we had the issue on some of the dimension series... Fan would run at full speed, for no reason, turns out the mobo in the few random machines had gone bad.