SATA Power Pinout: Fifteen Pins in Three Groups
Quick answer / TL;DR: Short answer: pins 1 to 3 carry 3.3 V, pins 4 to 6 are their ground return, pins 7 to 9 carry 5 V, pins 10 to 12 are ground, and pins 13 to 15 carry 12 V. Each rail uses three pins to share current, and each group is arranged voltage-then-ground. Pins 1 to 3 are the ones to isolate if a drive with Power Disable will not spin up.
Eight contacts, one wiring pattern: T568B with minimum untwisting.The SATA power connector arranges fifteen pins as three identical groups of five: a voltage pin cluster followed by a ground cluster, repeated for each rail. Understanding that repetition is the key to reading the pinout, because it explains why the connector can carry current that a single pin could not.
This matters when repairing a cable, adapting a Molex connector, or diagnosing a drive that will not spin up because a rail is present when it should not be.
The Full Assignment
Read from the keyed end of the connector. The pattern is regular, which is what makes the connector easy to inspect once the structure is understood.
| Pins | Signal | Notes |
|---|
| 1 | 3.3 V | rail one, positive | 2 | 3.3 V | parallel with pin 1 | 3 | 3.3 V | parallel with pins 1 and 2 | 4 | ground | return for 3.3 V | 5 | ground | parallel | 6 | ground | parallel | 7 | 5 V | rail two, positive | 8 | 5 V | parallel | 9 | 5 V | parallel | 10 | ground | return for 5 V | 11 | ground | parallel | 12 | ground | parallel | 13 | 12 V | rail three, positive | 14 | 12 V | parallel | 15 | 12 V | parallel |
The three-pin grouping is not redundancy for reliability. It spreads current across three small contacts so that no single contact carries more than about 1.5 A, which keeps contact heating within the connector's thermal limits.
Using the Pinout Diagnostically
With a multimeter on the drive side of the cable, each rail can be checked under load. This distinguishes a supply problem from a drive problem in a way that no software tool can.
- Pin 1 to pin 4: expect 3.3 V, often absent on modern supplies
- Pin 7 to pin 10: expect 5 V, within the ATX tolerance band
- Pin 13 to pin 4: expect 12 V, within the ATX tolerance band
- Any rail reading zero: check the supply end before suspecting the drive
- A rail that sags under load: cable gauge or connector resistance
The 3.3 V Isolation Trick
Drives that implement Power Disable stay off when 3.3 V is present. The standard workaround is to break the connection on pins 1 to 3 so that only 5 V and 12 V reach the drive.
| Method | How | Reversible | Risk |
|---|
| Molex to SATA adapter | no 3.3 V at all | yes, unplug it | low | Kapton tape over pins 1 to 3 | covers the contacts | yes, remove tape | low if applied carefully | Cut the 3.3 V conductors | permanent | no | damaged cable | Adapter with 3.3 V removed | built for the purpose | yes | lowest |
Real-World Applications
Testing a drive that does not spin up
Measure the rails first, then try a Molex adapter. If the rails are correct and the drive spins on the adapter, the 3.3 V rail is the cause. That sequence takes less time than any software diagnostic.
Repairing a damaged connector
A melted or discoloured housing indicates resistance at the contacts. Replace the connector or the cable rather than cleaning it. The pinout is standard, so a replacement from any supplier will match.
Custom power distribution in a mod or build
When making custom leads, keep the three-pin grouping per rail and match the conductor gauge to the load. Combining rails onto a single conductor defeats the current-sharing design and creates a hot spot.
Where the pinout does not apply
Slimline SATA uses six power pins rather than fifteen, and micro SATA uses nine. Neither follows the fifteen-pin assignment, and neither should be probed with the assumption that it does.
Related reading: How SATA power works overall — blogs/news/sata-power-cable
Related reading: Fifteen-pin compared with four-pin — blogs/news/sata-15-pin-vs-4-pin
Standards and Verification
The SATA power connector pinout, keying and electrical ratings are defined in the specification published by the Serial ATA International Organization. The 3.3 V, 5 V and 12 V rails and their tolerances correspond to the ATX power supply specification.
Note that the 3.3 V rail is optional in practice on most modern supplies, and many SATA power cables carry no 3.3 V conductor at all. A reading of zero on pins 1 to 3 is therefore normal rather than a fault, and it is why some drives with Power Disable work on one cable and not another.
For verification, measure at the drive connector with the drive connected and, where possible, during spin-up. Idle readings hide a rail that sags under transient load, which is exactly the condition that produces intermittent drive failures.
Photograph the connector before modifying it. Pins 1 to 3 are easy to identify in a photograph and difficult to identify by feel in a cramped chassis, and taping the wrong end will leave the drive without power entirely.
Frequently Asked Questions
Which pins are 12 V on SATA power?
Pins 13, 14 and 15. They are the third group, following the 5 V group and its grounds, and they feed the spindle motor on a 3.5 inch drive.
Which pins should I cover to fix a drive that will not spin up?
Pins 1, 2 and 3, which carry the 3.3 V rail that triggers Power Disable. Covering them with insulating tape is a reversible workaround; a Molex adapter achieves the same thing.
Is a missing 3.3 V rail a fault?
No. Many modern power supplies do not provide 3.3 V on SATA connectors, and most drives do not need it. A zero reading on pins 1 to 3 is normal.
How much current can each pin carry?
About 1.5 A. Because each rail uses three pins, the practical limit is roughly 4.5 A per rail, which is why the grouping exists.
Does the pinout apply to slimline SATA?
No. Slimline SATA has six power pins and micro SATA has nine. Their assignments differ, and probing them as if they were fifteen-pin SATA risks shorting a rail.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.
