Strange happening...........

Goose · Feb 15, 2016

Yesterday afternoon I ran my Dodge Grand Caravan into my shop with the intentions of installing a CB radio.

Besides the main power wire, this CB has an extra power wire that does nothing but hold the selected channel on the unit. If it's not connected, whenever you turn the radio on, it comes up on channel 9. I like to just leave it on channel 19.

The Caravan has two power outlets near where I planned on putting the CB, one hot all the time and one on and off with the ignition. At least for starters, I planned to plug the main power line into the outlet that goes on and off with the ignition, and plug the other line into the line that's hot all the time to hold the channel. I plugged the main line in and the CB worked OK but always came up on channel 9. When I plugged the other line in, the CB went dead, the other line got hot, and a few relays chattered under the dash. I immediately pulled the plug.

What happened, was on the lighter plug I'd used for the extra line had one wire with a white stripe that I assumed was the hot wire. It wasn't. The wire with the stripe was the ground. I switched the wires, plugged it back in, and found the entire electrical system was dead. I thought I'd blown a main fuse or breaker. I started checking things out and it dawned on me to check the battery. I put a load tester on the battery and found the battery was dead. I put my big charger on the battery and everything came back to life. I wondered if the battery had taken that exact moment to call it quits. (Two and a half year old Walmart battery with 3 years free replacement).

I left the charger on it for a half hour and the battery tested OK with a load tester. Everything was back to normal on the vehicle. I'd unplugged the CB. I let the vehicle set overnight and it started right up this morning, with apparently no damage done.

My question is, how could that small wire being plugged in with wrong polarity for no more than a few seconds kill the battery like that? It doesn't make sense.

jon f mn · Feb 15, 2016

Is it posible one of the battery cables was corroded or loose and hooking up the charger fixed that?

rbhuntn · Feb 15, 2016

(quoted from post at 08:10:36 02/15/16) Yesterday afternoon I ran my Dodge Grand Caravan into my shop with the intentions of installing a CB radio.

Besides the main power wire, this CB has an extra power wire that does nothing but hold the selected channel on the unit. If it's not connected, whenever you turn the radio on, it comes up on channel 9. I like to just leave it on channel 19.

The Caravan has two power outlets near where I planned on putting the CB, one hot all the time and one on and off with the ignition. At least for starters, I planned to plug the main power line into the outlet that goes on and off with the ignition, and plug the other line into the line that's hot all the time to hold the channel. I plugged the main line in and the CB worked OK but always came up on channel 9. When I plugged the other line in, the CB went dead, the other line got hot, and a few relays chattered under the dash. I immediately pulled the plug.

What happened, was on the lighter plug I'd used for the extra line had one wire with a white stripe that I assumed was the hot wire. It wasn't. The wire with the stripe was the ground. I switched the wires, plugged it back in, and found the entire electrical system was dead. I thought I'd blown a main fuse or breaker. I started checking things out and it dawned on me to check the battery. I put a load tester on the battery and found the battery was dead. I put my big charger on the battery and everything came back to life. I wondered if the battery had taken that exact moment to call it quits. (Two and a half year old Walmart battery with 3 years free replacement).

I left the charger on it for a half hour and the battery tested OK with a load tester. Everything was back to normal on the vehicle. I'd unplugged the CB. I let the vehicle set overnight and it started right up this morning, with apparently no damage done.

My question is, how could that small wire being plugged in with wrong polarity for no more than a few seconds kill the battery like that? It doesn't make sense.

Not sure which CB you are using but hooking up any transmitter radio to the power outlets in a vehicle is dangerous as this can cause electrical fires.

I am a Amateur Radio (HAM) operator and my degree is in Electronic Engineering. Whenever I hook any type of transmitter radio up in any vehicle I use 10ga wire with 15 amp fuses wired directly to the batt or a batt terminal under the hood. The fuses are at the batt connection also along with the fuses that are inline at the radio.

This ensures that there are two fuses on the hot wire and one of the ground. I have seen to many pictures of nice vehicles burned due to hooking up radios to the electric outlets in a car. The wires to these outlets are not heavy enough gauge to handle the AMPS that the transmitter requires. I also go to my local electronic supply store and get two of the ferrous core cable surrounds about 1 inch long and slip over the wire. One just after the batt and one at the radio to reduce the noise over the power cables from the alternator.

If you will hook up both HOT wires to the batt direct along with the ground you should have no more issues.

If you go this route look at the inline fuse on the power cable that came with the CB and use a 5 AMP less at the batt connections. This will allow the fuse at the batt to blow before the one at the radio. Fuses are cheap. Radios and cars are not.

I run HAM radios in my pickup that put out up to 50 watts and have never had any electrical issues with this setup.

Hope this helps.

notjustair · Feb 15, 2016

That's what I wonder. Did it heat something up that was near the fail point anyway? I wonder if you won't be heading down the road and hit a pot hole and it does it again.

Steve@Advance · Feb 15, 2016

That is really strange... No way you discharged a healthy battery with what you did, unless the bad connection was left that way for an extended time, like a couple days. If you had created a dead short, something would have smoked or taken out a fuse.

Possibly the battery was in the process of failing, sitting with the doors open while you worked on it may have drained it. I had a battery do that, if I ran the radio, had the doors open for even a half hour, the starter would barley crank, or need to be jumped. A new battery fixed it.

Goose · Feb 15, 2016

I wondered about that. The cables were clean, I'd just cleaned them and put stuff on them to prevent corrosion a couple of months ago. In the commotion, I removed the ground cable from the battery and reinstalled it. Maybe the connection was a bit loose. Guess I'll never know.

Goose · Feb 15, 2016

Bingo!

I had both front doors and both side sliding doors open for a good half hour while I sorted out wires on the CB and put the plugs on it. That could well have drained the batter significantly before I even plugged the CB in.

Thanks! I never thought of that.

jeffcat · Feb 15, 2016

Nope! One of my Fords did that. Some vehicles have a sensor for reverse polarity. If you hook the battery up backwards the car protects itself. Least that is what my mechanic friend told me. If you have the receipt get a new battery cause it is free.

M-MAN · Feb 15, 2016

My guess is you have one of those smart relay's that kill the power after 10 to 15 minutes if you leave something on when you get out & it tripped. My old Grand Marquis did that. They are supposed to reset themselves but mine never did. Give it a boost and she would fire off. Cut if off and she would fire right back up on her own.

jacksun65 · Feb 15, 2016

I had a CB that had been boosted every time I keyed up it threw a code in the computer.

Goose · Feb 15, 2016

I'm stumped. As the crow flies, my shop is a mile from I-80, so I have a CB antenna on top of the shop and sometimes I patch in a CB to a battery and listen to chatter while I'm working in the shop.

This afternoon, I set that CB unit on a bench and it checked out OK the way I have the plugs wired. Plugged the plugs into the Caravan and it did the same thing all over again. Drained the battery almost instantly. After I unplugged everything and put it on a charger for ten minutes everything was normal again.

Guess I'll forget about that particular CB in that Dodge. Funny thing is, that same CB worked fine hard wired into an Olds 88, and as I said it worked OK on the bench.

T in NE · Feb 16, 2016

I believe cobra radios come with a 2 amp
fuse. They make -3s?

T in NE · Feb 16, 2016

Run a fused power from the battery to the radio constant power wire. Then use the plug for the switched power, or find switched power to hardwire into.

If you want to be able to remove it quickly, get a pair of 3-pole replacement cord ends. One ground, one constant power, one switched, tuck it up under the dash somewhere.

Strange happening...........

Goose

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jon f mn

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rbhuntn

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notjustair

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Steve@Advance

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Goose

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Goose

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jeffcat

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M-MAN

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jacksun65

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Goose

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T in NE

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T in NE

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