I'm hooking up a CB in my 98 F150. I want it on switched power, but where on earth do you get it?

I found one spot with switched power going into a loose hanging relay box above the brake pedal. What is that relay box, and can I tap power from there?

 

Are you familiar with relays? You can install one from your radio's switched power or your fuel pump's switched power. Basically, it's not reccommended to tap into anything directly. For instance, lets say you wanted to tap into that brake pedal thing you found. You might not know for certain how much amperage it can handle and how much your CB requires. I have all kinds of crap inside my truck, what I usually do to have a safe and reliable connection is run power from the battery into a relay. Relays usually have 4 pins. 1 Pin is to connect to the (fused)battery and one to ground. The other two pins are used for switched power and to connect your accessory(in this case your CB). Basically, no power will be sent to your CB until the relay receives that signal from the switched power. The switched power will only come on when your ignition kicks on. Use a multimeter to find power that comes on when you power the ignition. Like I said the fuel pump and the radio are the ones I know of that are easily accessible. The fuel pump's inertia switch is located on the front passengers kick panel. You can rip that panel off and theres a bunch of wires. Use a multimeter to test some wires for current when you turn the ignition on. I believe the the switched power wire from the radio is red or yellow, test some of those. If you have an aftermarket radio, you can use the blue (often reffered to as remote) as switched power, mind you switched only when the radio is actually playing.

 

Put an add-a-fuse in a slot that is hot in the run / accy position ( like the radio fuse slot ).



This will give you power any time the radio can run, that is not added to the factory harness.

The relay under the steering column is the blower motor relay and the other should be the flasher.

 

Fuse taps are great, but they add load to an existing circuit. I was hoping for circuit that wasn't already being used. The problem is, the radio takes X amps, and the wiring for the radio circuit in the truck is 16 gauge. Adding a CB that transmits up to 40w could almost triple the load on that circuit, not to mention be a direct source for noise interference between two audio devices.

I'm talking like what GM does... they have a slot in the fuse panel that is dedicated with its own supply pin and fuse just for adding accessories. Is there a circuit like that in my F150?

 

Very familiar... but wiring relays is a pain the butt... and you still have to find a suitable hot source that isn't already loaded. Are you saying that Ford doesn't have a circuit built in? I've never encountered that before. Every vehicle always has a circuit that is set up for law enforcement or fleet use to add a radio or lighting, or other accessory. My 95 F250 had one, and every GM, toyota, mercedes, BMW, AMC, and dodge that I've owned built since about 1945 has had one. Its hard to believe that a 98 Ford doesn't.

I just find it hard to believe that I have to wire a relay, tap into a random switched source, AND run a hot wire all the way from the engine bay, when on every other vehicle I know its so much simpler than that.

 

No, add-a-fuses don't add the amps to an existing circuit, they create a new circuit.
It is taking the hot in run / accy feed that is in the truck already and making a new circuit from that feed.
A normal CB is 4 W output, and has a 5 W input power requirement.
If you want to call the 40 W xmt on the antenna side 5:4 ratio on the power usage of the CB, then this is 50 W power requirement for the CB radio, which at idle is 3.97 A for the CB.

While the wire to the radio may or may not be 16 AWG, you are not putting the load on the radio circuit itself ( the reason for the add a fuse ). The circuit you are adding the amp draw to is the hot in run / accy postion wire in the fuse panel, which is sized for more then just the radio itself.

If you are using an add-a-fuse so it adds the amperage to the radio circuit ( which it is not, only to the radio fuse itself ), then you are installing it backwards




You have not looked at a modern GM, Nikki's G6, there is no such thing.
I had to use a hot in run position to trigger the fuzeblock.com fuse block to add the heated seats to her G6.
This is true of all 3 fuse panels in the car.
Same for both my Dodges, a 90 & 95, no fuse to a lead.

The new F250s have an upfitter panel, that is the relay and fuses already setup, but this is what the other post suggested you do. This was started in 2005 ?

Not real sure where you get the idea all vehicles are setup for law enforcement use, they also do the same thing, trigger a relay and run a separate fuse panel. There is too much on a squad to have a single fuse running it.

If you think it is easier then this, good luck, and please post back the route you took, as I would be interested to learn something new.

 

I appreciate everyone's help, but I guess I asked the wrong question. I don't think that every vehicle is set up for law enforcement use, nor did I say that. I'm not an idiot. Perhaps I didn't make my question clear.

Let's wipe the slate clean because I kinda feel like I'm being treated like a kid. I know what I'm doing, I can wire a relay, and I can use a fuse tap. I know how, so let's skip that for now. Ironically, one of my jobs at the hot rod shop is building custom wiring harnesses, but you guys have no way of knowing that.

I just find it hard to believe that almost all vehicles on the road HAVE an expansion circuit built in (including your G6, sscully; grn/blk wire behind the dash fuse panel in a grey connector according to alldata) except the F150. Its a vehicle that was used so heavily in fleets that I can't believe there isn't a circuit to add on a slave panel.

I was asking the question the way I did because I figured there HAD to be that circuit somewhere I was to dumb to find it.

SScully - the reason I don't like fuse taps for additional circuits (except when used to trigger a relay) is that it adds load to the fuse panel. I know it doesn't add load to the radio circuit, but it adds load to the bus supplying the switched side of the fuse panel. It adds load to the wire supplying the fuse, not the circuit after the fuse. Its also a very "dirty" source for audio. When you're transmitting 40w of amplitude modulated signal, it gets dirty quick. The radio is far from "normal." 1969 hot finals with the plan to go MOSFET in the future. It deadkeys 12w and swings 40w. RMS is probably around 25w.

But I didn't want to get into that. I just had a simple question; where do you guys get your acc power?

I got my answer and consider the matter closed.

 

I found 12v key on power on this wire, i used a relay, so this wire i only pulled "trigger power" to the relay. Honestly not sure where the wire goes to, but it worked just fine, and i got everything tucked back behind the kick panel.




(black and green wire)

2003 XLT Super Crew

 

If he uses the add a fuse like the post above yours he will be fine, it has two fuses for it, one for the radio or what ever he tapped into and a fuse just for the cd or other devide. So it there is to much load it will blow the one fuse and the other will be fine.