Gentex’s GENFDM3LN Full Display Mirror (FDM®) is a technologically advanced rearview mirror designed for both standard auto-dimming functionality and an integrated display for rearward vision. This device represents a significant evolution in automotive safety and driver convenience. The installation and operation of the FDM require careful adherence to technical specifications and step-by-step procedures to ensure optimal performance and safety.
This article provides a detailed overview of the installation process, operational modes, and troubleshooting tips for the Gentex GENFDM3LN. The information is derived exclusively from the manufacturer’s official instruction manual and technical documentation. Readers will find a clear explanation of tools needed, mounting procedures, power harness routing, and calibration steps. Additionally, this guide outlines the different modes of operation—mirror, display, and reverse—and offers insight into display adjustments and advanced features such as secondary camera input.
Installation Overview
The installation of the Gentex GENFDM3LN involves a series of precise steps to ensure proper integration with the vehicle's electrical system and mechanical structure. The mirror is designed for compatibility with a wide range of vehicles, though specific adaptors may be necessary depending on the make and model.
Tools and Preparation
Before beginning the installation, the following tools are required:
- T20 Torx screwdriver
- Pliers
- Foam tape
- Wire ties
- Measuring device or smartphone with angle-finding capability
The installation process should begin with the vehicle turned off and the negative battery cable disconnected to prevent electrical shock or damage to the vehicle’s systems. The factory rearview mirror is typically removed by loosening the T20 Torx screw at the base and sliding the mirror upward toward the headliner. In some cases, removal of the A-pillar or other body panels may be necessary to access the mounting area.
Mounting the Full Display Mirror
Once the factory mirror is removed, the Gentex GENFDM3LN is mounted by sliding the mirror mount over the windshield button. The T20 Torx set screw should be tightened to a torque of 13.3–17.7 in-lbs. It is important to note that specific vehicle adaptors may be required for secure mounting.
After securing the mirror to the windshield, the mirror power harness must be connected to the mirror’s connector. This harness should then be routed to a location where 12V ignition and ground lines are accessible. The routing should be secured with foam tape and wire ties to prevent movement or damage.
Power Harness Connections
The installation requires a 12V switched ignition line and a ground supply. These are typically found in the A-pillar, junction block, or overhead compartment. T-taps should be used to connect to these lines, and it is essential that the t-taps are securely snapped together to ensure a stable connection.
Once the power harness is connected and secured, the mirror is ready for testing and calibration.
Mounting the Camera
The camera is a critical component of the FDM system, providing the video feed for the display mode. Proper mounting of the camera is essential for a clear and unobstructed view.
Choosing the Mounting Location
The camera should be mounted as high as possible inside the vehicle, ideally between the defrost lines and within the wiper path to ensure an unobstructed view. It should be centered in the vehicle and never mounted on sliding or moving glass. A suitable window bracket should be selected based on the measured angle of the windshield:
- 17°–29°: Sports cars and sedans
- 30°–54°: CUVs
- 55°–90°: SUVs and trucks
The mounting location should be cleaned thoroughly to ensure optimal adhesion of the two-way tape. It is important to avoid oils or debris on the surface to prevent poor adhesion.
Securing the Camera
To mount the camera, the two-way tape liner should remain attached during the dry fit. The camera bracket should be held in place to test the chosen location. Once the location is confirmed, the liner is removed, and the bracket is pressed firmly onto the rear glass. The mirror should be installed when the temperature is above 50°F to ensure proper adhesion.
After the bracket is mounted, the camera is adjusted vertically so that the horizon appears in the upper third of the mirror display. The set screws on the camera mounting bracket should be tightened, but over-tightening should be avoided to prevent damage to the components.
The camera cover is then installed using two T-15 screws. As with the bracket, care should be taken not to over-tighten the screws.
Operational Modes and Adjustments
The Gentex GENFDM3LN operates in three primary modes: mirror, display, and reverse. Each mode serves a distinct purpose and can be activated through the toggle switch at the base of the mirror.
Mirror Mode
In mirror mode, the FDM functions as a standard auto-dimming rearview mirror. This mode is activated by pushing the toggle switch forward toward the windshield. The mirror automatically detects glare from trailing vehicles and adjusts its dimming level accordingly to preserve driver vision during nighttime driving.
To test the auto-dimming function, the forward-facing sensor can be covered with a dark cloth or cardboard. The mirror should dim after a few seconds, depending on ambient light conditions. Once the dimming function is verified, the mirror can be adjusted to its standard driving position.
Display Mode
Display mode is activated by pulling the toggle switch toward the driver. This illuminates the LCD display, providing a real-time, wide-angle video feed from the rearward-facing camera. The display mode allows drivers to see an unobstructed view of the area behind the vehicle without the need to look over their shoulder.
To ensure optimal display quality, the camera should be aimed so that the image is level and centered. The display may initially appear rotated, but the product is equipped with an auto-rotate feature that will adjust the image over time. Within the first 30–60 minutes of driving, the image should stabilize and appear level.
Reverse Mode
If the vehicle is equipped with a reverse gear, the FDM can automatically switch to reverse mode when the vehicle is placed in reverse. This provides a specialized view of the area directly behind the vehicle, enhancing safety during parking or maneuvering in tight spaces.
Display Adjustments
Fine-tuning the display is important for ensuring a clear and comfortable view. The tilt of the mirror can be adjusted up or down to center the image. While the image may initially appear rotated, the auto-rotate feature will correct this over time. Users should refer to the quick reference guide for detailed instructions on adjusting the display settings.
An optional feature allows for the use of a secondary camera via an NTSC input. To activate this feature, the mirror must be placed in mirror mode, and the farthest button to the right must be held for 23–27 seconds. This will activate the RCD display. The secondary camera is triggered by 12V to pin 8.
Troubleshooting Common Issues
Despite careful installation and adjustment, users may encounter issues with the Gentex GENFDM3LN. The following troubleshooting tips can help resolve common problems:
Excessive Glare in Display Mode
If the mirror display shows excessive glare or reflects the interior of the vehicle, it should be switched back to mirror mode by pushing the toggle switch forward. The mirror head should then be readjusted to ensure a clear rearward view. Once the mirror is properly adjusted, it can be switched back to display mode.
Hazy or Foggy Display
In certain weather conditions, the rear glass may become foggy with condensation, resulting in a hazy or foggy display. In such cases, the mirror should be switched to mirror mode until the glass is clear. Activating the rear defroster can help eliminate fog and restore clarity to the display.
Obstructed or Out-of-Focus Display
If the display appears obstructed or out of focus, the mirror should be switched to mirror mode until it is safe to inspect the camera and the rear of the vehicle. Obstructions such as dirt, water droplets, or physical objects should be removed to ensure a clear view.
Grainy Display at Night
During nighttime driving, the camera may display a grainy image due to a lower frame rate. This is a normal operating condition and does not indicate a malfunction. The camera is designed to adjust its frame rate based on ambient light conditions to provide the best possible image.
Warranty and Support
The Gentex GENFDM3LN is backed by a 36-month limited warranty, covering defects in materials and workmanship under normal use. Users who encounter technical difficulties or need assistance with installation or operation should refer to the official Gentex website for support and additional resources.
Conclusion
The Gentex GENFDM3LN Full Display Mirror represents a significant advancement in automotive rearview technology. By combining traditional auto-dimming functionality with a high-quality LCD display, it enhances both safety and convenience for drivers. Proper installation, including precise mounting of the mirror and camera, is essential for optimal performance.
Users should follow the step-by-step installation instructions carefully, ensuring that all electrical connections are secure and that the camera is mounted in a location that provides an unobstructed view. Regular calibration and adjustments may be necessary to maintain a clear and accurate display.
Troubleshooting common issues such as glare, fog, and graininess can be addressed through simple adjustments and maintenance. The optional secondary camera feature adds an additional layer of flexibility for users seeking expanded rearview capabilities.
Overall, the Gentex GENFDM3LN is a reliable and user-friendly solution for drivers looking to enhance their visibility and driving experience. With proper installation and care, this advanced mirror system can provide years of reliable service.