2020 Isuzu NQR Bulb Sizes: Headlight, Tail Light, and Fog Light Guide

As an ASE-certified master technician, I know firsthand that when you’re dealing with a commercial workhorse like the 2020 Isuzu NQR, downtime is not an option. Whether you are running local deliveries, managing a fleet, or operating a specialized box truck, maintaining proper visibility and DOT compliance is critical. Burnt-out headlights or tail lights can lead to failed inspections and unsafe driving conditions, especially given the heavy payloads these cab-over trucks carry.

Below is your comprehensive bulb size guide for the 2020 Isuzu NQR, covering everything from the headlights down to the license plate lights.

Quick reference

Depending on the specific upfitter and whether your truck was spec'd with composite aerodynamic headlights or the basic work-truck sealed beams, sizes can vary slightly. The N-Series generally relies on industry-standard, heavy-duty halogen bulbs.

Note: Box trucks and upfitted chassis often use custom rear lighting setups provided by the body manufacturer (like Morgan or Supreme). Always verify your tail/brake light housings if your NQR has a custom rear body.

LED vs halogen upgrade considerations

Upgrading to LED bulbs is highly recommended for commercial vehicles due to their extended lifespan and resistance to vibration—a huge plus for the stiff suspension of an Isuzu NQR. However, keep these factors in mind:

• CANBUS Errors and Hyperflashing: The electrical system on the 2020 NQR is straightforward, but swapping standard turn signal bulbs (1156/1156NA) to LEDs will almost always result in hyperflashing. You will need to wire in a 50W 6-ohm load resistor for each LED turn signal bulb or install a heavy-duty LED flasher relay.
• Headlight Housing Scatter: If you upgrade your H4 halogen headlights to LED, ensure you purchase bulbs with a precise diode alignment. Cheap LEDs in a reflector housing will scatter light, blinding oncoming traffic and reducing your actual road visibility.
• Voltage Specifications: Ensure any aftermarket LED replacements can handle standard 12V automotive systems with potential alternator spikes up to 14.5V.

How to replace each bulb

Here are a few quick tips from the shop floor for replacing bulbs on the N-Series cab-over:

• Headlights (Low/High Beam): The cab-over design actually makes this quite easy. You can access the rear of the headlight housings by opening the doors and looking behind the front corner panels, or by tilting the cab forward. Unplug the harness, remove the rubber dust boot, unclip the retaining wire, and swap the H4 bulb.
• Front Turn Signals / Corner Lights: These are located just above or beside the main headlamp cluster. You typically need a Philips screwdriver to remove the housing screws, allowing the corner assembly to pop forward for bulb access.
• Rear Tail / Brake / Reverse Lights: If your NQR has the factory Isuzu frame-mounted tail lights, simply remove the two to four Phillips screws on the lens cover. Swap the 1156 or 1157 bulbs by pushing in and twisting counter-clockwise.
• Cab Clearance / Side Markers: Removing the two small screws on the amber/red lenses gives you direct access to pull the 194 wedge bulbs straight out.

Common lighting issues for this generation

The 2020 Isuzu NQR is remarkably reliable, but commercial use takes a toll:

1. Vibration-Induced Failures: The stiff ride of an unladen NQR can rattle standard incandescent bulb filaments to death. Upgrading to heavy-duty (Long Life / LL) halogens or quality LEDs is the best fix.
2. Corrosion in Rear Housings: Rear tail lights mounted under the frame are constantly exposed to road spray and salt. If a new bulb doesn't fix your brake light, check the socket for green corrosion. Apply dielectric grease to all new bulb bases to prevent this.
3. Grounding Issues: If multiple lights in the rear cluster act up simultaneously (e.g., tail lights dimming when turn signals are on), you have a bad chassis ground. Trace the ground wire from the rear harness to the frame and clean the contact point.

Commercial trucks require proper maintenance to stay on the road and out of the DOT weigh station penalty box. If you need professional help chasing down a short, fixing a damaged wiring harness, or performing general maintenance, don't leave it to chance. Find a trusted shop on Repairius.