So I have hardwired my V1 into at least 7 cars at this point. I am struggling at the moment to figure out why something isn't working this time. My latest car is the SAME make and model as my last, which really doesn't matter but I thought I'd throw it out there.
I use the hardwire kit, tap into ign-switched power and get a good ground, and I ran a standard phone cord up to the detector itself. It powers on perfectly, no issues. When I put in the remote display, I opted to make my own cord from a CAT5 cable, and put RJ11 connectors on the ends using just 4 of the wires in the cable (I work in IT and I make network cables all the time). The wires are reversed in order from end to end, as they would be in a standard RJ-11 phone cord. Yet when I turn the key to ignition, the display doesn't light up.
I am now suspecting the cord to the detector is not telling it that there's a display, since THAT cord is a standard phone cord and I think it only has two wires.
Is this plausible?? I am confident in my wiring and crimping, and in fact it's really nice to have the EXACT right length cords going places in the car. I used CAT5 since I have a ton of it laying around, so it's well protected and certainly provides adequate power. I think I will soon be making a new wire for the detector itself...