LC and LG are internal motherboard headers typically used for connecting front panel LEDs and buttons, with LC often referring to “LED Control” and LG to “LED Ground” or similar signaling.

Overview

Motherboards feature numerous internal headers that allow the case's front panel components—such as power buttons, reset buttons, and indicator LEDs—to interface with the motherboard . Among these, LC and LG connectors are usually associated with LED indicators:

• LC (LED Control or LED Connector): This pin or header provides the signal that controls the LED, such as the power-on LED or hard drive activity LED. It carries the voltage or pulse that turns the LED on or off depending on system activity .
• LG (LED Ground): This pin serves as the ground reference for the LED circuit, completing the electrical path so the LED can function properly . These headers are part of the front panel header block, often labeled as F_PANEL or similar in motherboard manuals. They are usually small, two-pin connectors, and their correct orientation is important: reversing the polarity may prevent the LED from lighting, though it generally does not damage the motherboard.

Practical Use

When building or upgrading a PC:

1. Locate the front panel header on the motherboard, usually near the bottom edge.
2. Identify the LC and LG pins using the motherboard manual or silkscreen labels.
3. Connect the corresponding LED wires from the case: the positive wire to LC and the negative wire to LG.
4. Verify functionality by powering on the system; the LED should light according to its intended function (power, HDD activity, etc.).

Additional Notes

• LC and LG are not universal labels; some manufacturers may use PLED+, PLED-, or similar designations for the same purpose.
• These headers are distinct from other internal connectors like USB headers, fan headers, or audio headers, which serve different functions .
• Always consult the motherboard manual for exact pinout diagrams to avoid miswiring. Understanding LC and LG headers ensures that your front panel LEDs operate correctly, providing visual feedback for system status and activity.