I'm planning on replacing the garage coach lights at my house. We have a junction box on the inside of the garage, directly behind where the fixture is mounted however it's behind the plywood / cedar clapboards. This is my question:
The wires for the fixture are not long enough to pass through from the outside of the garage to the box on the inside wall. The wires are about 4 or 5 inches and I probably need at least 10 or 12 inches. Plus, the fixture should be properly mounted on some time of box. I've purchased the outside mounting box shown in the images I've included. Question: Should I use 18 gauge wire from splices in the outside mounting box and connect them with splices in the inside junction box or should I use 14 gauge wire for this connection between the two boxes? Keep in mind that there isn't a lot of room in the outside mounting box. Also, for the ground, can I also use similar 14 gauge wire to extend the ground to the inside box. The fixture takes a max of 2 60 watt lights however will most likely be using LEDs
Images showing outside fixture mounting product is not my house rather its from the product listing.
Images of the fixture and boxes:
Thanks for any help / guidance.