PSU for bench testing automotive parts

[basslover1]

I have an extra PSU from my HTPC, http://m.newegg.com/Product/index?itemnumber=N82E16817139049

That one to be exact, and I'm wanting to use it for an automotive project I'm working on that will allow me to test parts at my desk instead of in my car.

I know that I need to use a jumper from one of the grounds to the on cable, which I've done. The PSU successfully turns on. But I've run into a problem.

Using my multimeter to test the lines on the molex plugs, I get around +5v on the red wire, but sadly -3v on the yellow wire, which should be 12v.

Why? What am I missing? Every video I've watched on how to use a PSU for automotive testing simply says jump a ground to the on wire, test for 12v and you're good to go.

Any help?

 

[Layer8]

To run an ATX power supply stand-alone, you need to short PS_ON# with GND (Standard colors: green and black, pins 13 and 14 an the ATX connector).
That's it.
That was not possible on old AT supplies, but that does not apply to your unit.

Did you by chance measure the orange (3.3V) wire in reverse?
What voltage has the gray (PWR_OK) wire?

One thing I'd like to mention: Automotive parts should be tested with 13.8V, the voltage in your car when the motor is running.

 

[basslover1]

To run an ATX power supply stand-alone, you need to short PS_ON# with GND (Standard colors: green and black, pins 13 and 14 an the ATX connector).
That's it.
That was not possible on old AT supplies, but that does not apply to your unit.

Did you by chance measure the orange (3.3V) wire in reverse?
What voltage has the gray (PWR_OK) wire?

One thing I'd like to mention: Automotive parts should be tested with 13.8V, the voltage in your car when the motor is running.

Yea I already had the power_on pin jumped to ground and the psu turns on I just couldn't get proper voltage on the molex connections.

It doesn't matter though, I was able to get the 12V I needed directly from the 24 pin plug. Probably not ideal but I was only testing lights so not a serious load for the PSU.

Thanks though.