2018 Subaru Forester Bulb Sizes

Quick Reference: 2018 Subaru Forester Bulb Sizes

The 2018 Subaru Forester offers a range of lighting options across its trim levels, from traditional halogen setups to more advanced HID (High-Intensity Discharge) and LED systems. Understanding these differences is crucial when considering replacements or upgrades.

For example, the low beam headlights commonly use an H11 halogen bulb on most trims. However, certain higher trims (often those equipped with projector-style headlights) feature a D4S HID bulb, which provides a significantly brighter and whiter light output. The high beam headlights consistently use an H9 halogen bulb across all trims. Fog lights, where equipped, typically take an H11 halogen bulb.

Daytime Running Lights (DRLs) saw a split in the 2018 Forester lineup. Lower trims like the Base and Premium often utilize a 168/194/T10 halogen bulb, while higher trims such as the Sport and Touring frequently come with integrated LED DRLs, which are generally not user-serviceable as individual bulbs.

Turn signals, both front and rear, utilize a 7440A amber halogen bulb. The "A" in 7440A signifies amber, which is essential for proper signaling. Brake lights and tail lights share a dual-filament 7443 red halogen bulb. The 7443 functions as both a dimmer tail light and a brighter brake light when activated. Reverse lights across all trims commonly use a 921 halogen bulb.

For interior and auxiliary lighting, the license plate lights, front side markers, and map lights typically use a 168/194/T10 halogen bulb. The dome light usually takes a DE3175 halogen festoon bulb.

LED vs. Halogen Upgrade Considerations

Upgrading from halogen to LED bulbs in your 2018 Subaru Forester can offer enhanced brightness, a modern look, and increased longevity. However, there are important factors to consider:

• CANBUS Errors: Many modern vehicles, including the 2018 Forester, use a CANBUS (Controller Area Network Bus) system to monitor vehicle electronics, including lighting. LED bulbs draw significantly less power than halogens. This difference can cause the CANBUS system to detect a "bulb out" error, leading to flickering, partial illumination, or dashboard warning lights. To prevent this, "CANBUS-ready" LED bulbs or load resistors (decoders) are often required. Load resistors simulate the electrical load of a halogen bulb, tricking the CANBUS system into thinking the correct bulb is installed.
• Adapters and Fitment: While many LED bulbs are designed to be direct replacements, some applications may require specific adapters or modifications to ensure proper fitment and beam pattern, especially in headlight housings. Always check for compatibility and ensure any aftermarket LED has a proper heat sink to dissipate heat, as LEDs are sensitive to high temperatures.
• Beam Pattern (Headlights): For low and high beam headlights, simply swapping to LED bulbs in a housing designed for halogens can result in a scattered light pattern, reducing visibility for you and potentially blinding oncoming drivers. Projector housings (often found with HID systems) tend to handle LED upgrades better than reflector housings, but careful research and beam pattern testing are still recommended.

How to Replace Each Bulb

Replacing bulbs on your Forester often requires basic hand tools and patience. Always ensure the vehicle is off and the lights are cool before attempting any bulb replacement.

• Headlights (Low/High Beam) & Fog Lights: Access is usually from behind the headlight assembly in the engine bay. You may need to remove a plastic splash guard or move the battery/airbox for easier access on some models. Twist to remove the old bulb, disconnect the electrical connector, and connect/install the new bulb, ensuring it's seated correctly.
• DRL (Halogen): Often accessed with the high beam or turn signal bulb. Twist the socket out of the housing, pull the old bulb straight out, and push the new one in.
• Front Turn Signals/Side Markers: Similar to DRLs, usually found in the same housing as the headlight. Twist the socket out, remove the old bulb, and insert the new one.
• Rear Turn Signals/Brake/Tail/Reverse Lights: Access is typically found by opening the rear hatch and removing a panel inside the trunk to get to the back of the tail light assembly. Twist out the desired bulb socket, pull the old bulb, and insert the new one.
• License Plate Lights: These are usually accessed from the outside, often by removing a small screw or prying a plastic cover near the license plate.
• Dome/Map Lights: Carefully pry off the lens cover with a plastic trim tool or a small flathead screwdriver (wrapped in tape to prevent scratches). The bulbs usually pull straight out or unclip.

Common Lighting Issues for This Generation

Owners of the 2018 Subaru Forester may occasionally encounter a few lighting-related issues:

• Premature Halogen Bulb Burnout: While not exclusive to the Forester, some owners report halogen bulbs (especially headlights or fog lights) burning out sooner than expected. This can sometimes be attributed to vibrations, voltage fluctuations, or even touching the glass of the bulb during installation (oils from your skin create hot spots).
• DRL Malfunctions (Halogen): The halogen DRL bulbs, being lower wattage, can occasionally fail, leading to a "DRL out" warning. This is typically a straightforward bulb replacement.
• Tail Light/Brake Light Outages: Like any vehicle, the dual-filament 7443 bulbs can burn out, leading to either a lost tail light or brake light function. Always check both filaments when replacing.
• Interior Light Failures: While less common, interior bulbs can also burn out. Always check fuses if multiple interior lights cease to function simultaneously.

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