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How can I dim my Comp II LED gauges?

2-1/16" Gauges
The 2-1/16" Comp II LED gauges feature a single snap-in LED bulb. You can dim the lighting by reducing the voltage to the bulb (white wire).

A 1W 300ohm resistor installed inline on the white wire to each bulb gives a good level of dimming. Use a higher value resistor for dimmer light, a lower value resistor for brighter light.

3-3/8" Speedo and Tachometer
The 3-3/8" Comp II LED speedo and tachometer have integrated LED lighting. To dim the lighting on these gauges you need to reduce the voltage to the ACC connection (NOT the light wire). A 1W 100 ohm resistor installed inline on the ACC (12VDC) connection to the gauge gives a good level of dimming. Use a higher value resistor for dimmer light, a lower value resistor for brighter light.

Important notes when dimming the 3-3/8" Comp II LED gauges:

  • If your resistance value is too high, the gauge may not get enough power to operate. If this happens, reduce the resistor value.
  • When dimming the lighting with a resistor make sure the 12V+ "Always On" is connected to an unreduced voltage source, i.e. connect the "Always On" connection to either the 12V+ battery or to the main 12V ignition supply.

Can I use the Marshall dimmer switch to dim the Comp II LED gauges?
The dimmer switch is designed to work with the SCX gauge sets but can be adapted for use with the Comp II LED gauge sets. To use it with the Comp II gauges you will need to have the gauge backlight ON at all times (day and night) for the dimmer to work correctly on the 2-1/16" Comp II LED gauges. To use the dimmer switch with the Comp II LED gauge sets connect the output of the dimmer switch as follows:

  • 2-1/16" Gauges: Connect output of dimmer to the positive light wire.
  • 3-3/8" Gauges: Connect output of dimmer to the 12V ACC connection. Also, connect the white light wire to 12V ignition source so backlight is on when gauge is on. When dimming the 3-3/8" gauges make sure that the BATT+ connection has 12V+ connected. You can either use a direct connection to the battery 12V+ (always on) OR 12V+ power from the ignition circuit (only on when the vehicle is on).

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