[ 1. The power supply's fan is not turning.
  2. The +/- 12 volt lines on the motherboard are not on their own the cause of the fan not turning (but could be a second problem - multiple shorted caps).
  3. There is no adequate load to test the power supply independently (to see if the fan turns). ]



What Now?

We will now make some resistance measurements.
You will need a digital multimeter, and the knowledge of how to use it to make resistance measurements.

IMPORTANT:

Do NOT use the continuity setting on your multimeter.  Use the resistance setting.

1. Turn off the power supply.

2. Disconnect both P8 and P9 from the motherboard.




3. On the motherboard, measure the resistance between the ground line and the +5 volt line.

On the many good 5150/5155/5160 motherboards that I have, this measurement ranges in value from about 200 ohms up to about 1300 ohms. If your motherboard measures zero or a few ohms, then there is definitely a short-circuit on the +5 volt line. In either case, click HERE

4. On the motherboard, measure the resistance between the ground line and the -5 volt line.

On the many good 5150/5155/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading. If your motherboard measures zero or a few ohms, then there is definitely a short-circuit on the -5 volt line. In either case, click HERE

5. On the motherboard, measure the resistance between the ground line and the +12 volt line.

On the many good 5150/5155/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading. If your motherboard measures zero or a few ohms, then there is definitely a short-circuit on the +12 volt line. In either case, click HERE

6. On the motherboard, measure the resistance between the ground line and the -12 volt line.

On the many good 5150/5155/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading. If your motherboard measures zero or a few ohms, then there is definitely a short-circuit on the -12 volt line. In either case, click HERE

So you did not measure any shorts (or partial shorts) on the motherboard's power lines.

CONCLUSION:

Because:
1. there are no motherboard shorts, and
2. the power supply's fan is not turning,
the logical deduction is that the power supply is faulty.