Originally Posted by xie67
Okay you can use a old 12v fan to cruedly check for voltage presence as so follows:
Cut off the molex plug so you have two bare cable ends.
Just connect one end of the fan cable (the black) into the BLACK on the PSU molex and the remaining fan cable into the YELLOW for 12v the RED for 5v and the ORANGE for 3.3v
Obviously as the voltage measured is lower the fan speed will decrease.
As I stated this is a very crued way to check for voltage to be present at the connectors but if you got no multimeter it's your best bet and to avoid embarrasment at the store front.
BTW : if you are using a fan with LED's in it observe the polarity of the leads