How To Install Holley RetroBright LED Headlights Into A Four-Eye Fox Mustang

10 min read

How To Install Holley RetroBright LED Headlights Into A Four-Eye Fox Mustang

10 min read

Light-emitting diode (LED) technology is gradually replacing standard filament light bulbs in every industry—and for good reason. They use less power and are brighter than old-school incandescent bulbs. Vintage cars are a great application for LED technology. Aged wiring, worn connectors, tired alternators, and elderly bulbs are a recipe for dim, unsafe headlight performance.

Holley's RetroBright LED headlights are designed to bring your classic car into the light, so to speak. They're available three color temperatures: "Modern White" (5700 Kelvin), "Classic White" (3000 Kelvin), and a European-inspired "Yellow Lens."

To sample how these new-fangled headlights work in a classic application, we installed a quartet of Holley's 4" x 6" Classic White headlights (p/n LFRB120) in a 1986 Saleen Mustang. 1979-1986 four-eye Fox Mustangs are an ideal application for Holley's RetroBright technology, as the alternators in these earlier Fox Mustangs are notoriously sketchy. Add nearly four decades of age, and the reliability of converting to LED headlights is a no-brainer.

For applications like this 1986 Mustang, the benefits of Holley's RetroBright LED headlights include:

• brighter, broader light spread for improved safety and visibility

• replaces foggy and pitted headlights for a clean, crisp appearance

• less current draw enhances reliability and longevity of the alternator, wiring, and connectors

• remote plug keeps connections away from bulb heat

• much longer life than a typical halogen bulb

• LEDs brighten more quickly for better flash to pass visibility

While Holley's RetroBright LEDs are a direct bolt-in for the original 4" x 6" sealed beam headlights, the wiring might require a bit of finagling on some applications. Fortunately, the Holley RetroBright headlights come with an adapter harness. On this 1986 Mustang, we had two wiring options: use the included adapter harness or modify the factory harness to fit. We'll cover both for this installation to show you how easy it is to convert an old Mustang to Holley's RetroBright LED headlights.

RetroBright Mustang Install 1

Holley's RetroBright LED headlights are available in three color temperatures (5700K, 3000K, and European-inspired Yellow). Each light includes instructions, an adapter harness, and terminals to cover just about every wiring situation.

Retrobright Mustang Install 2

To convert this 1986 Mustang to Holley's RetroBright LED headlights, we chose four 4" x 6" 3000K lights (p/n LFRB120).

Retrobright Mustang headlight lens removal

We started the installation process by removing this Saleen Mustang's headlight covers.

RetroBright Mustang headlight bezel removal

Then, we removed the four screws and the headlight bezels.

RetroBright Mustang high-beam removal

With the bezel removed, we unplugged the factory harness from the high beam bulb.

RetroBright Mustang low-beam removal

Next, we removed the low beam bulb.

RetroBright Mustang oem plug

The OEM harness and plug were in good condition, but the terminal positions differed from the Holley RetroBright plug.

Retrobright Mustang high-beam oem plug

The high beam plug only had two terminals.

RetroBright Mustang multimeter testing

We had a wiring diagram for our Mustang, but we used a multimeter to verify the positions and polarity of the high and low beam wires...just in case.

RetroBright Mustang adapter 1

There are two ways to wire up the Holley RetroBright LED headlights. One method uses the included adapter harness.

RetroBright Mustang harness 2

Using the included instructions, we assembled the adapter harness with the terminals in the correct positions to match our Mustang's OEM harness.

RetroBright Mustang adapter 3

Another option is to disassemble and re-pin the factory connector to match the Holley RetroBright plug. While this solution uses less wiring, be mindful that the factory wiring will be altered, and it won't work with a standard replacement halogen bulb any more.

RetroBright Mustang adapter 4

We chose to re-pin the factory harness so the Holley RetroBright harness plugged right in.

RetroBright Mustang Bucket Fit

The Holley RetroBright housing fit the factory bucket and bezel just like the standard headlight.

RetroBright Mustang high-beam adapter 1

For the high beam, we also had two wiring choices. If we removed the low beam terminal from the Holley RetroBright headlight, it plugs directly to the factory harness.

RetroBright Mustang high-beam adapter 2

The other option is to use the included adapter harness but remove the low beam terminal per the instructions.

RetroBright Mustang high-beam adapter 3

We used a small flat blade screwdriver to remove the blue (low beam) wire from the adapter harness.

RetroBright Mustang high-beam install 1

We chose to use the adapter harness on the high beam side rather than permanently alter the Holley RetroBright plug to fit the OEM connector.

RetroBright Mustang hi-beam reinstallation

We installed the Holley RetroBright bulb using the factory bezel and hardware.

RetroBright Mustang light spread pattern comparison

Compared to the factory-style halogen bulb (left) the Holley RetroBright lights are brighter and the beam spread pattern is wider. Nice!

Retrobright Mustang early Fox Mustang interface

1979-1986 Mustangs have a "graphic warning module" that alerts drivers of malfunctioning lights. It compares voltage in each light circuit to the supply voltage. If the voltage differential is too low, it assumes a light is burned out. Since our Holley RetroBright headlights drew less current than the factory bulbs, the voltage in the headlight circuit was high enough to trigger the warning light.

RetroBright Mustang early Fox Mustang graphic interface 2

Rather than deal with a false warning light, we located and removed the headlight circuit voltage sensing wire from the connector behind the graphic warning module. (On this 1986 Mustang, it was the brown wire with a blue stripe.)

RetroBright Mustang early Fox Mustang graphic interface 3

We taped off the loose wire and labeled it for future reference.

Retrobright Mustang lights off

Even when off, the Holley RetroBright LED headlights gave this mustang a clean, crisp appearance that's similar to OEM…but better.

RetroBright Mustang full on

The Holley RetroBright LEDs are significantly brighter than the OEM halogen bulbs, but draw less current—perfect for this Mustang's vintage electrical system. We also found the high beams flash on and off more quickly for better flash-to-pass performance. That's a win-win!


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