Molex wiring disaster - anyone help?

9 Feb 2007
Hi everyone, have been around for a while, but am afraid my first post is typed in a panic.

I did something as simple as adding a fan to my PC. Computer unplugged, connected fan, plugged in computer, switched on. Everything began the start up process, then this horrible screeching sound started and the computer switched off again. I hit the power switch at the back as soon as I could.

On inspection of the fan, the wires were incorrect going into the molex.

So it should have been:

power supply yellow to fan red
power supply black to fan black

But instead it was wired:

Power supply yellow to fan black
Power supply black to fan red

I'm now scared to switch my pc on again. Has this happened to anyone before? Or has anyone got enough electrical knowledge to tell me what effect this would have?
1 Sep 2005
Scottish Highlands
The yellow wire is the 12v line, the red wire the 5v and the 2 black wires are earth. My best guess is that feeding the earth line on the fan might have burnt the fan motor out. Can't see it doing a huge amount of damage to anythign else though. Unplug the fan and see if the computer still works ok.