The Princeton Tec, FUEL headlight is known to have the battery door latch break when replacing the batteries. If your lamp is under warranty, you can send your lamp in for repair or, in my case, they will send you replacement doors.
This Instructable shows how to replace the battery door.
NOTE: I mention several times throughout the following steps to be careful. Considering that the plastic latch snapped and other owners have had failures due to the plastic breaking on the latch or the head strap/band mount, I fear that one could easily damage the light while trying to replace the battery door.
Please consider how thin the plastic is in the areas where force will be applied during this repair and take care to not damage your light beyond repair.
Step 1: Remove the Strap and Strap Mount
Carefully remove the strap, take care not to break the ends of the strap mount. I have read where another owner has broken the tabs where the strap is inserted.
Using a small screw driver, remove the two screws that attach the strap mount to the light.
Remove the strap mount by sliding it towards the battery door end of the light, while carefully lifting the end of the mount that is away from the door. This will help to lift the arched friction lock (molded into the strap mount) out of it's slot so that the mount can slide towards the battery door end of the lamp and be removed.
Step 2: Remove Broken Battery Door
Using a small pin (I used the end of a small paper clip), gently push out the Hinge PIN of the old broken door. Again, be careful not to use excessive force that may break the PIN mounts on the light housing. Hold the case firmly, to prevent the case halves from trying to separate while pushing the PIN out.
Push the PIN out just enough to grab it with pliers and then gently pulled it out completely from the opposite side.
Pictured is the new battery door and a new Hinge PIN that I received from Princeton Tec.
Step 3: Install the New Battery Door
Gently insert the new Hinge PIN into one side of the mounts on the light housing (I did this with the door sitting in place and using my fingers to prevent breaking the tab on the housing).
Push the PIN slightly into the area where the door will be located.
Insert the door over the PIN and push the PIN into the door.
Using pliers, gently press the Hinge PIN flush into the mount on the light housing.
Step 4: Optional - Reshaping of the Latches
Optionally, In an attempt to relieve some stress on battery door latch and hoping to prevent future failure of the latch, I decided to remove some material from the latch on the battery door and from the tab on the light housing.
Slowly, remove some material from the inside of the battery door latch and create a slight bevel to help make it easier to open the battery door during battery changes. From the factory the door latch doesn't appear to be beveled and opening the latch is quite stiff, requiring excessive force to open the door.
I also beveled the latching tab on the housing and rounded edges slightly.
These modifications help to ease the opening and closing of the battery door and yields less flex of the door latch, which should help prevent future failure.
Step 5: Reattach the Strap Mount and Strap
Slide the strap mount back into the mounting tabs while making sure the friction lock is inserted back into its slot in the light housing. Replace the two screws for the strap mount.
Insert strap into the mount, again being careful not to break the slots where the strap is inserted.
Install a fresh set of batteries and enjoy.
Step 6: Conclusion
After contacting Princeton Tec support, I had to contact them two or three more times to request a status update on the parts. I used email, calling them may get better results. Finally the parts were shipped to me. In the package, I received three new doors and new hinge PINs.
I hope my modification to the latch will help prevent or possibly delay future failure. With two extra doors on hand I should get at minimum, a few more years of use from my FUEL light.
I like the Princeton Tec brand, but in the future I will inspect the quality and design of the moving parts more carefully before purchase.
I hope this Instructable has helped you.
Thanks for viewing.