What is the low beam headlight bulb size for a 1979 Mercury Marquis?

The 1979 Mercury Marquis uses a H4656 bulb for the low beam headlights. We recommend upgrading to LED for better visibility.

What is the high beam headlight bulb size for a 1979 Mercury Marquis?

The high beam bulb size for the 1979 Mercury Marquis is H4651.

Why are my 1979 Mercury Marquis headlights dim?

Dim headlights on a 1979 Mercury Marquis can be caused by aging halogen bulbs, which lose brightness over time, or oxidation (cloudiness) on the plastic headlight lenses. Upgrading to a H4656 LED conversion kit can provide a significantly brighter and whiter light output.

Which bulb fits the 1979 Mercury Marquis fog light?

The 1979 Mercury Marquis typically does not come with factory fog lights in all trim levels. If your vehicle is equipped with them, check the manual as sizes can vary by trim.

Is the 1979 Mercury Marquis single or dual beam?

The 1979 Mercury Marquis uses a dual bulb headlight system. This means you have separate bulbs for high and low beams.

Can I install LED bulbs on my 1979 Mercury Marquis?

Yes, the 1979 Mercury Marquis comes with standard halogen bulbs from the factory, but they can be upgraded to LED. You will need a H4656 LED conversion kit for the low beams.

Did the 1979 Mercury Marquis change headlight bulb sizes from the previous year?

Yes — the 1979 Mercury Marquis uses different bulb sizes than the 1978 model. The 1979 generation introduced this bulb configuration.

Is the 1979 Mercury Marquis the first or last year to use H4656 bulbs?

The 1979 Mercury Marquis is the only year in the 1979 generation to use the H4656 bulb for the low beam headlight.

How do I change the headlight on a 1979 Mercury Marquis?

Turn off the vehicle and open the hood. Locate the headlight assembly from behind, remove the dust cover or retaining clip, disconnect the wiring harness, twist the old H4656 bulb counter-clockwise to remove it, then insert the new bulb and reassemble. The whole process typically takes 10 to 30 minutes per side depending on accessibility.

Are LED headlights legal for a 1979 Mercury Marquis?

LED bulbs used off-road or in auxiliary lights are legal everywhere. For on-road headlight use, legality varies by state. Many states allow LED retrofits as long as the beam pattern meets DOT standards. For the best legal compliance, choose a DOT-approved H4656 LED kit that is designed as a direct replacement and produces a proper cutoff pattern without excessive glare.

How much does it cost to replace 1979 Mercury Marquis headlights?

A pair of halogen H4656 bulbs costs $15 to $40, while LED conversion kits run $25 to $60 per pair. If you have a shop do the work, expect an additional $20 to $50 in labor per bulb. Replacing them yourself at home saves the labor cost and usually takes under 30 minutes.

What is the difference between halogen and LED for a 1979 Mercury Marquis?

Halogen bulbs produce a warm yellow light (around 3200K), last 500 to 1000 hours, and draw more power. LED bulbs emit a brighter white light (5000-6000K), last 25,000+ hours, and use less energy. LED upgrades for the H4656 position are available as direct plug-and-play replacements.

The 1979 Mercury Marquis has a unique bulb configuration not shared with adjacent model years.

Fitment Guaranteed for 1979 Mercury Marquis

What Size Bulbs Does a 1979 Mercury Marquis Use?

Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.

Installation Difficulty

Easy (Plug and Play)

Est. Replacement Cost

$15 - $40 (Halogen) / $30+ (LED)

What Lighting System Does the 1979 Mercury Marquis Have?

Owners of the 1979 Mercury Marquis will find a total of 10 lighting elements throughout the vehicle's exterior. It features a comprehensive lighting system powered by a dual-bulb halogen configuration using separate H4656 low beam and H4651 high beam bulbs for precise light distribution. This model belongs to the mid years of the Marquis's 1967-1986 production span.

Can You Put LED Bulbs in a 1979 Mercury Marquis?

Upgrading to LED is one of the most effective ways to modernize your Mercury's appearance and safety profile. We recommend starting your upgrade with the H4656 low beams, as they see the most use. Adding a matching H4651 LED kit later will complete the look and ensure consistent lighting performance.

1979 Mercury Marquis Bulb Size Chart

Position	Bulb Size	Shop
Turn Signal Front	1157A	Buy 1157A →
High Beam	H4651	Buy H4651 →
Low Beam	H4656	Buy H4656 →
Brake Light	1157	Buy 1157 →
License Plate	194	Buy 194 →
Side Marker	1157	Buy 1157 →
Parking Light	1157A	Buy 1157A →
Turn Signal Rear	1157	Buy 1157 →
Tail Light	1157	Buy 1157 →
Reverse Light	1156	Buy 1156 →

How do the 1979 Mercury Marquis's bulbs compare to other years?

The 1979 Mercury Marquis changed bulb sizes from 1978. The previous model year used a different configuration.

The 1980 model switched to a different bulb configuration.

This bulb configuration covers the 1979 model years. ← 1978 1980 →

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Other Marquis Years

1986 1985 1983 1980 1978 1977 1976 1975 1974 1972 1971 1970 1969 1968 1967

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