Question for the electrical (vehicle) gurus?

SpydieFan · #1

Howdy folks...

Long story short, I got a new CB radio for my pickup and I'm selling my old one to a friend. I always wire my CB to my battery, however he wants his on a cigarette lighter plug so he doesn't have to run wires :confused: ... anyway...

I wired a cigarette lighter plug onto the end of the two lengths of CB power and ground cord. There is an inline fuse (3A) on the CB power cord, there is a fuse in the cigarette lighter plug (10A) and the cigarette lighter outlet itself is fused (20A). Here is the problem...

I plugged the setup into the cigarette lighter, boom, inline fuse blows. Trying to figure out what was up, I put a 10A fuse in it (had nothing else on hand).

Next the cigarette lighter plug blows. I replaced that with the proper 10A fuse again. Plugged it back in, turned the knob on the CB to on, and then my 20A fuse going to the pickup blows.

Now I'm no electrical newbie, but I mostly deal with vehicle lights (marker lights, off road lights, etc) where they're all done with relays and fused switches... however this one has me stumped.

What say you, electrical guru of Spyderco Forums? :D

Donut · #2

(Excuse me that I'm blurbing and thinking out loud, it is not very organized.)

I'm thinking something got messed up in the CB when the 3A fuse blew. (I'm thinking it shorted.) The CB came with a 3A fuse? I do know that you can buy fast blow fuses and slow blow fuses, and a slow blow fuse will offer your equipment less protection than the fast.

I don't think the cigarette lighter plugs are designed to handle a lot of power. In my experience, I see very small wire running to them. Wikipedia says they are rated to handle 10 amps. I think that if a car has a 20 amp fuse serving a cigarette lighter and the cigarette lighter is protected by a 10 amp fuse, that means other things are also connected to the 20 amp fuse.

If you take a look at Power Inverters, once you get to a certain power rating (which I will admit, is probably nowhere near the power rating of a CB), they give you lugs to use instead of a cigarette lighter.

I "think" a CB can consume around 50 watts, which should be around 4 amps.

mattman · #3

Something is shorted.
20 amps is a lot of current... does the CB chassis smell acrid?

xceptnl · #4

mattman wrote:Something is shorted.
20 amps is a lot of current... does the CB chassis smell acrid?

That was my first thought. Possibly the ground and power leads for the CB were wired in reverse, this is what caused the initial fuse (3A) to blow. Then the 10A probably allowed enough amperage to fry a capacitor in the board of the CB. Check the wiring in the CB plug that you added. It may be too late, but I think that seems like the most logical place to start.

w3tnz · #5

I would firstly check the polarity of the circuit and make sure that it's correct, I've also seen cigarette lighter plugs blow fuses because of poor connection, but in that case you would notice a lot of heat and wouldn't happen instantly. Due to the size of the fuses your blowing it sounds like a short circuit or reverse polarity. You might also want to consider splicing into the wires behind the lighter and hard wire it.

SpydieFan · #6

w3tnz wrote:I would firstly check the polarity of the circuit and make sure that it's correct, I've also seen cigarette lighter plugs blow fuses because of poor connection, but in that case you would notice a lot of heat and wouldn't happen instantly. Due to the size of the fuses your blowing it sounds like a short circuit or reverse polarity. You might also want to consider splicing into the wires behind the lighter and hard wire it.

"I always wire my CB to my battery, however he wants his on a cigarette lighter plug so he doesn't have to run wires ... anyway..."

I would directly wire it if it were mine... however...

I will check the polarity though, that makes the most sense to me.

Thanks