Molex 4-pin Peripheral Pinout
Classic 4-pin 'Molex' drive power connector supplying +5 V and +12 V.
Overview
The 4-pin peripheral connector (Molex 8981, universally called a 'Molex') is the long-standing PC power connector for hard drives, optical drives, fans, and accessories. It carries +12 V, +5 V, and two grounds.
Standard wiring is pin 1 +12 V (yellow), pins 2/3 ground (black), pin 4 +5 V (red). Chamfered corners polarize the mating.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | +12V | POWER | +12 V supply (yellow wire) |
| 2 | COM | GND | Ground (black wire) |
| 3 | COM | GND | Ground (black wire) |
| 4 | +5V | POWER / VIDEO | +5 V supply (red wire) |
Notes
- Pin 1 = +12 V, pin 4 = +5 V - the reverse of the Berg floppy connector.
- Housing corners are keyed (two chamfered) so it mates only one way.
Reference: Molex 8981 series / PC power supply connector reference· verified 2026-06-27