Klein Tools VDV501-851 Cable Tester Kit with Scout Pro 3 for Ethernet / Data, Coax / Video and Phone Cables, 5 Locator Remotes

So it's a number of things. First and foremost, you'll wanna figure out where in the house all the ethernet and coax terminate. In the IT world we call this a Main Distribution Frame (MDF), in the homeowner world we call it "that place with a bunch of random wires coming out of the ceiling (or wall)." If you're lucky, both will terminate to the same place. If not, all the Ethernet will terminate at one place, and the coax at another - very likely the coax is in a box on the side of the house that might be zip-tied shut by your ISP. There is no harm in opening this box, and you can take the time to replace the zip ties with a weatherproof lock to make things a bit prettier and more manageable. But once you know 100% you have found both ends of the Ethernet and Coax cables (individually) then use this bad boi to test them: https://a.co/d/0igGX3Ze I picked one up for a very similar project a few years ago, and it's a godsend. I recommend picking up some sort of labeling (could be anything from a dedicated label printer to just a basic Avery label sheet) to label/number the cables on both ends so you know what goes where. Regarding the faceplate: https://a.co/d/0aR0k81s this is just an example, you don't have to buy a 10-pack and can probably find an individual one at Home Depot for like $2. You'll also need some cables to go along with that tester: - Ethernet Cables: https://a.co/d/00MFzC2k - Coax Cables: https://a.co/d/02TT2WH1 Depending on where the ethernet and coax cables lead you may need a dedicated switch and splitter respectively but that's getting out of scope for your request. Hope this helps!

100mbps isn't a symptom of improperly-grounded shielding. You have an open conductor or short between two conductors, probably on the blue or brown (using 568B sequencing) pairs, most likely on pin 8 (solid brown). From your description, it sounds like you bought a 150ft patch cable and cut in half then re-terminated. What AWG wiring was used in the patch cable? If it was smaller than 23AWG, the conductors might not be wide enough for the connector contacts to reliable pierce into the conductor. Note that larger AWG numbers result in thinner diameter conductors. It's also possible that a mismatch between the crimp die and connector could result in poor crimps. I currently use the Ideal FT45 crimper (as part of this kit) and also own the Klein VDV226-110, which are both great, (but don't do a lot of shielded cable runs). A network cable tester such as the Noyafa NF-8209S or Klein Scout Pro 3 would help you identify the problem. Both have TDR function that can show the distance to the fault (though Noyafa's is easier to use). Noyafa adds a crimp QC test to show if all the pins on a connector are making contact with the conductors.