Hello,
This may not be the best place to ask this, but general forums said 'non-technical'.

This question is going to be vague, because I don't have the specifics. So I understand if the question can't be answered.

My power supply has a string of 2 leads that say 'fan only' on it.
Only the 12v and ground wires are in the string.
I plugged my 120mm fan into it, and it doesn't spin up.
The lead coming from the fan only has the 12v and ground wires hooked up.
The wires do match up in the molex connector. It's not like the 12v is in the 5v spot.
However, if I hook the fan lead up to a normal connector that has 12v and 5v connectors, it works fine.

Any thoughts?

What make/model of power supply? I always have to google for online documentation to figure stuff like this out. It might be for a special fan like a graphics card fan or a CPU fan...

No idea about the make/model, I bought it almost a year ago.
I'll find out when I get home and reply here.

In regards to the fan, it came with the case, so it's a no-name.
The case is a 4U server case with 4 5.25" drive bays on each side.
One side just pulls air through the drive bays for cooling.

Maybe the 2 wires from the Power supply were never connected internally. Do you have a multimeter/voltmeter to test that you're getting 12V? Or maybe it's current is so limited that it can't turn on a 120 mm fan.

Haven't really messed with my server until now.

I hooked it up, the fan jerked a lil, but didn't spin up.
it's like there would be enough power to run it, but not start it up.

The PSU is a 430watt Antec TPII-430

That kind of cable should connect to the motherboard for sensing the RPM of the power supply fan. May not work though.

The black wire is ground and the blue (I think) is the sensing wire. The middle pin and the black wire is for powering a fan.

Antec power supplies are crap. Power supplies from Eneramax, Power & Cooling, Seasonic are excellent brands.