What is the low beam headlight bulb size for a 1978 Dodge Diplomat?

The 1978 Dodge Diplomat 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 1978 Dodge Diplomat?

The high beam bulb size for the 1978 Dodge Diplomat is H4651.

Why are my 1978 Dodge Diplomat headlights dim?

Dim headlights on a 1978 Dodge Diplomat 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 1978 Dodge Diplomat fog light?

The 1978 Dodge Diplomat 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 1978 Dodge Diplomat single or dual beam?

The 1978 Dodge Diplomat uses a dual bulb headlight system. This means you have separate bulbs for high and low beams.

Can I install LED bulbs on my 1978 Dodge Diplomat?

Yes, the 1978 Dodge Diplomat 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 1978 Dodge Diplomat change headlight bulb sizes from the previous year?

Yes — the 1978 Dodge Diplomat uses different bulb sizes than the 1977 model. The 1978 generation introduced this bulb configuration.

Is the 1978 Dodge Diplomat the first or last year to use H4656 bulbs?

The 1978 Dodge Diplomat is the only year in the 1978 generation to use the H4656 bulb for the low beam headlight.

How do I change the headlight on a 1978 Dodge Diplomat?

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. Note: Dodge vehicles use a CANbus system, so LED replacements may need an anti-flicker decoder. The whole process typically takes 10 to 30 minutes per side depending on accessibility.

Are LED headlights legal for a 1978 Dodge Diplomat?

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 1978 Dodge Diplomat 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 1978 Dodge Diplomat?

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. Since the Dodge uses CANbus monitoring, choose a CANbus-compatible LED kit to avoid dashboard errors.

The 1978 Dodge Diplomat has a unique bulb configuration not shared with adjacent model years.

Fitment Guaranteed for 1978 Dodge Diplomat

What Size Bulbs Does a 1978 Dodge Diplomat 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 1978 Dodge Diplomat Have?

The 1978 Dodge Diplomat utilizes a refined lighting configuration featuring 10 distinct bulb positions. 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 early years of the Diplomat's 1977-1989 production span. Note that Dodge vehicles typically feature a CANbus electrical monitor that checks for specific bulb resistance.

LED Flicker Warning

This vehicle is known to use a CANbus system. Installing standard LEDs may cause flickering.

Use a CANbus decoder.

Can You Put LED Bulbs in a 1978 Dodge Diplomat?

Upgrading to LED is one of the most effective ways to modernize your Dodge'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. Because Dodge utilizes a CANbus system, standard LED bulbs may cause "bulb out" errors on your dashboard. Always opt for "Error-Free" or CANbus-ready kits which include the necessary resistors.

1978 Dodge Diplomat Bulb Size Chart

Position	Bulb Size	Shop
Turn Signal Front	1157A	Buy 1157A →
Side Marker	168	Buy 168 →
High Beam	H4651	Buy H4651 →
Low Beam	H4656	Buy H4656 →
Tail Light	1157	Buy 1157 →
Reverse Light	1156	Buy 1156 →
Parking Light	1157A	Buy 1157A →
License Plate	168	Buy 168 →
Brake Light	1157	Buy 1157 →
Turn Signal Rear	1157	Buy 1157 →

How do the 1978 Dodge Diplomat's bulbs compare to other years?

The 1978 Dodge Diplomat changed bulb sizes from 1977. The previous model year used a different configuration.

The 1979 model switched to a different bulb configuration.

This bulb configuration covers the 1978 model years. ← 1977 1979 →

Finding the best installation guide...

Other Diplomat Years

1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979 1977

Other Vehicles That Use H4656 Bulbs

1992 Chevrolet Camaro 1992 Chrysler New Yorker 1991 Chevrolet G10 1991 Chevrolet Van 1991 Chrysler LeBaron 1991 Ford Country Squire