Route power cables easily

Jim, KF4NBG, shared this on the HamRadioHelpGroup list today:

My club had a fox hunt yesterday, a group of us were standing around chatting and I mentioned that I was trying to find a car stereo system installer to route the power wiring from the battery to the cab.  One of the guys spoke up and said that he installed systems in cars for 15 years and showed me exactly where to run the wire.

It seems that most if not all foreign and some American cars have an automatic transmission, but when they form the body parts they stamp out the space for the clutch pedal to go through the firewall since it doesn’t cost any more to have the hole there.  He looked under the dash, sure enough the space was there and very easy to get to, he also showed me where it will come out in the engine compartment.   All I have to do is drill a hole, put a rubber grommet into the hole and run the two wires.

Hope that this tip helps you and saves you a few dollars as well.



  1. David Brodbeck N8SRE says:

    That’s an excellent tip. I have two more options that are no-drill solutions:

    – In cars that are equipped with air conditioning, the A/C refrigerant pipes usually are surrounded by two large rubber or foam boots where they pass through the firewall. These usually go directly into the passenger side footwell area, under the dash, and usually cover holes that are much larger than the actual A/C plumbing. I’ve sometimes poked a small hole in the boot and fed wire through. If you keep the hole smaller than the wire it will form a good seal. Note that condensation sometimes forms on these pipes so make sure any drips can’t follow the wire down to your equipment!

    – In some cars, the main wiring harness goes through a large, molded grommet with a separate molded ‘teat’ for each wire. Sometimes there are extra ‘teats’ that you can use just by cutting the tips off and stuffing your new wire through. I try not to use this area for RF wiring because of its proximity to the car’s other wiring, though.

    Also, many cars include stampings in the passenger side firewall to accommodate the clutch and brake pedals in countries where they drive on the other side of the road. On at least one car I owned, these were actually pre-drilled and plugged with rubber plugs; it was as simple as popping out one of the plugs and popping in a grommet.

    The lesson here is there’s often an easy way to run a wire where you need one to go, if you peek around with a flashlight for long enough!

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