When hardwiring your dash cam, you may have notice some black plastic cylinders on the wire which has a glass tube inside and wondered what that piece is. The hardwire kits for our BlackSys, LG Innotek, and Thinkware dash cams all have this sort of cartridge on them. The cigarette cables for a number of dash cams actually have them too, Blackvue's 12V cigarette cable actually has two of these, one in the plug and one just a few inches upstream of the plug. These are glass fuses that add additional protection for your camera in case there is a short that could damage the camera.
Most dash cam manufacturers use a 6mm x 30mm fuse which should be available at your local electronics DIY/hardware store should they need to be replaced. The most common rating we've seen is 2A 250V but other fuses are available, if you have to go up or down slightly there shouldn't really be any issues. The above picture shows the difference between a good glass fuse and a burnt one. With the good one you can see the wire that goes all the way through from one end to the other. The bad one is burnt so you can see how the electricity wouldn't be able to flow from one end to the other.
Generally speaking it's rare for these fuses to blow and less than 0.1% of our customers have this issue. But if one power cable works while another one doesn't (e.g., hardwire kit vs. cigarette cable) it may be worth checking these fuses. The glass fuses are fairly easy to open/switch out and no special tools are required. Some customers have asked us if they can remove these fuses altogether as it may be difficult to tuck this plastic holder in their trim, you can definitely do this but do so at your own risk. If you are familiar with splicing, it's possible to move the plastic holders downstream so they aren't in the way of your install.