dcgrosvold

Hey all -

I am planning to install a CB rig and a HAM radio in my '14 JKUR soon. I want to have the CB and HAM radio on switched 12V power. Here's my thinking:

I already have a 12V tap for the cig lighter circuit. Could I use that to switch a 40A relay that would then power the CB and HAM radio? Is there anything inherently wrong with this? I am wondering if the relay coil would draw too much power from the Cig lighter circuit. I would still plug my cell phone into the cig lighter so that would draw 2A at any rate. I'd hate to overload that circuit.

Let me know what you all think and if there are other ways to do this that might be easier.

Dave
KG5MWH

ronjenx

The relay coil will draw very little current.

Here is a better way to get switched power: Easy Switched Power Source

dcgrosvold

Cool! Thanks for that, ronjenx!

Rogue26

The front power port is fuse M6 and is a 20amp fuse. That is more than enough for your accessories and a relay coil. Since it is close to where you will be installing your accessories I would use it. That will also keep the integrity of your fuse box intact.

14Sport

Since you have to run the power wire for pin 30 into the tub anyway it wouldn't be a big deal to run a second switched one at the same time and not cut into the factory wire. You should be fine either way though as the control circuit draws milliamps as mentioned so your choice. If you use the cig lighter make sure it is one with a picture of a key on it's cap. Also, check the draw of the two radios and if you have room to beef up the power wire a bit then you could use a SPDT relay instead of a SPST relay and then have an unswitched feed (pin 87A) separate from factory wiring in the tub in case you need it later.

dcgrosvold

14Sport - Yes. If I had to cut a wire, I would probably use the Fuse Tap suggested by Ronjenx. But I already have a tap that plugs between the power connector on the back of the switched cig lighter on the dash control stack, and the existing power harness. It includes a 10A fused harness that you can then use to power a CB, HAM radio or something else. Given the mods I'm planning to make, I will already have the dash apart anyway, and I can simply tie this to pins 85 & 86 on a 30A or 40A relay so the coil will be powered when RUN/ACC is enabled. I can then run a 12ga power lead from the battery to the relay contacts, and then run from pin 87 to the CB and HAM with separate in-line fuses. Like you say, I would then have pin 87A available for later use. I am planning to power an 8" Samsung Galaxy Tablet and Go Pro at a later time, so I'm thinking a dual-output SPST Relay sounds like it will work nicely. And like Rogue26 says, I would not have to compromise the integrity of the fusebox that way.

Thanks all for helping me think this through.

14Sport

Sounds like a plan but I wouldn't run a 10A fuse to power a control circuit. Switch it to a three or even a one.

Do you know the draw of the radios? How long is the longest part of the circuit going to be from the battery to the relay to the radio to ground? The longest run is what you want to use in your wire size calculations. It sounds like you know what you are talking about so I'm sure you're good but I would be remiss not to mention it.

ronjenx

10 amp fuse is fine as long as the wire can safely carry more than 10 amps.

14Sport

That's true but I prefer my fuses to blow sooner rather than later. I want to know if more current is flowing though that wire than expected, even if the wire can handle it. I match the fuses to the draw and play it close. I size my wire and relays to not be at risk.

dcgrosvold

Yeah. Good point on the control fuse. The harness I have came with a 10A fuse, since it was intended to power a CB or HAM radio w/o a relay. Since I what am planning will ultimately create more power demands than that can handle, I decided to go with a relay to carry the radio power and if necessary, any extra I might need for tablet, Go Pro, etc. I suspect a 30A or 40A relay would most likely handle everything up front that I would throw at it, but you never know.

I've no intention of overloading the system. I haven't determined the ultimate power draw yet, but I'll be sure to size the power leads accordingly. I'm starting with the CB this coming month, with a mobile HAM following soon after that. Just had the Samsung tablet delivered today. the GoPro will be a ways down the road.