Greetings, all. I'm wondering if anyone has any experience getting power from the battery under the hood into the cabin? I am an amateur radio operator looking to accomplish this. I went poking around last night, and there seems to be some sort of insulation, which I assume is for sound down by the feet of the passenger.

And, on a somewhat related thought, has anyone ever had experience getting the headliner down? I'd like to install some NMO antenna mounts in the roof. My experience has been with Jeeps and the more public safety-related vehicles where it's pretty common and/or well documented.

 

Is there a reason you can't tap into one of the fuses in the cabin fuse box? Would be easier than trying to run a separate tap directly into the battery.

 

I can't give you specifics since I haven't done it on an RX but I've pulled wires through a number of firewalls including the firewalls of both of our current Toyotas. Look in the engine compartment for a large bundle of wires coming through a grommet in the firewall. That will tell you where to look in the interior and what interior components might have to be removed or at least pulled back (i.e. carpet, insulation) to expose the interior surface of the firewall. I usually find the large wire bundle on the driver side in the area behind/above the brake pedal or gas pedal. The "tool" I use to get wires through the firewall is always a straightened wire coat hanger. I push the tip of the coat hanger from the engine compartment through the grommet into the interior by the large wire bundle, tape the wires I want to pull to the coat hanger, and then pull the coat hanger and the wires attached to it into the engine compartment. You probably already know how to do this if you've done it on Jeeps.

I once suggested to an amateur radio buff that he use a magnetic or fender mount antenna instead of drilling the roof and he responded with an emotional lecture on why a drilled roof mount antenna is the only acceptable option. Is the roof area above the rear interior dome light too far back? If not I wonder if removing the dome light would allow you to drill without removing the headliner and if you could push/pull the antenna cable over to and then down one of the door pillars without dropping the headliner.

If you google "how to remove a lexus headliner" you'll find a number of videos and websites with information but I didn't find any specific to the gen 4 RX. Here's a link to a video that shows how to remove door pillar trim:
Interior panels on vehicles made by Toyota are held in place mainly by plastic clips and a few screws. Plastic pry tools are very important for preventing damage.

 

Doing that typically is just asking for a ton of problems including RFI with the vehicle's computer system. Typically speaking, the interior fuse panel just doesn't have enough power. (Need about 30 amps to run a 110w radio.)

I was planning doing that method. I was hoping that someone might already know where the grommet is. How close to the Highlander are these vehicles? Poking around on those forums, there appears to be a very accessible grommet where the left foot of the front passenger would most likely be. I'm wondering if these are pretty similar in that respect?

As for antennas, your friend is correct. The only real way to do it is to drill. Mag mount antennas really don't work in long-term applications from both the vehicle and radio stand points. The rear mounts - though convenient - don't work as well as the drilled antennas.

 

Firewall grommet location can vary among vehicle models manufactured by Toyota but are generally in similar locations. I've run wires through the firewalls of many vehicles of various makes and have always easily found grommets through which I could pull wires.

The attached diagram appears to show two large grommets on the 2017 RX firewall. It might be easier to investigate this from the interior since it can be difficult to find a grommet by looking behind mechanical components in the engine compartment. I pulled several wires through a driver side grommet of our 2014 Sienna which is mechanically similar to the gen 3 RX and Highlander. I found that it was easier to locate the grommet I needed from the engine compartment if I pushed a straightened coat hanger though the grommet from the interior into the engine compartment. If you have difficulty finding the end of the coat hanger in the engine compartment, have a helper wiggle the coat hanger from the interior while you look for it in the engine compartment.

 

I know im bringing this back from the dead, but how did you get that diagram? I tried going to that site, but there are not diagrams, only a list of part numbers.