tawm

I'd like to run a DC power lead (12 gauge wire pair with fuse) straight from the battery into the passenger compartment of my 2008 RX 350. Does anyone have experience with / suggestions for running a cable through the firewall (any particular grommet available)?

The power lead is for a ham radio transceiver, the reason for a direct DC connection to the battery (rather than tapping a 12 VDC lighter socket) is to avoid the RF noise from the alternator, car circuits, etc.

I searched but couldn't find any previous posting. Any advice / suggestions appreciated. Is this a DIY? Thanks.

tfischer

I can't help you specifically, although in the past I have just looked to see where holes and grommets were available. Since you only need two lines, there should be something, although the sophisticated construction and high level of sound proofing may make this a little more difficult than it was on my '49 Ford coupe.
My only real tip: don't drill.

MMS4MSU

Look behind the glove box, there is a factory grommet with a group of wires through the firewall. If looking at the engine compartment from the front bumper, the grommet and wires are midway down about a foot & half to 2 foot left of center. I removed the air filter and box to pull the wire from the passenger side. I was running a amp wire for a sub so I am not sure if this location would cause interference.

tawm

Thank you both for your quick replies. I will drop the glove box and look. A friend with an RX300 said he found a grommet there. I wonder how much DIY I should try -- esp with routing the wires around the engine compartment to the battery and ensuring no chafing!

kitlz

It can be done. My installer had to hook up the extra equipment to the battery. Never had a problem in 5+ years. Good luck.

salimshah

There should be un-switched 12v in the cab area, but if you want to run a new wire you can through a unused spot in the grommet. You can expose it by removing plastic splash shield in the driver side wheel. The grommet is way up in the corner (driver left knee) .. almost close to the bottom of the windshield.

I like it as it is a straight shot from the battery. Double check if the spare hole can accommodate 12 gauge.


Salim

tawm

Thanks Anita, Salim and friends. My lovable local LX dealer (who charges $95 for an oil change!!!) estimates their installers would take 2 hours to do the job. I think I'll shop around and look for an experienced installer who can run: 1) the power leads as well as 2) a coax lead for the antenna out to the front trunk lip. $250 plus tax is kind of stretching it I think.
If any other hams online have suggestions / experience in terms of running RF coax and power leads thru the same grommet, please lemme know!
Thanks.

salimshah

Standard rule is to keep your supply and signal far away from each other or cross them at 90degrees.

I can assure you the left side grommet would be a tight fit for 12gauge. I dont remember the gauge, but I only had to pass a signalling relay wire (>12g).

I would suggest visit a audio shop and talk to the tech. It is very unlikely that they would have an RX experience, but worth a brief talk.

Salim

kiwi

its tight, but i ran a 8 gauge wire through the firewall just above the brake pedal. there is a main group of wires there with lots of room for more.

i will warn, it is very tight, especially on the engine side

tawm

Thanks Kiwi and Salim. A Lexus tech said their installers used the driver's side grommet to run wires, but a friend with an RX300 said for power / coax agreed the glove box side grommet would have more room. I'll explore it a bit. Thanks again to all who shared their knowledge!

salimshah

Ooops .. I just realized I am posting this in 2nd gen forum. Mine is a 300, so things may be different (really they may not be that different)

Salim

robincross

I am running antenna cable through the firewall in my 2014 CT200h.
What did you end up doing???