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Gregg121 · 01-19-2018, 08:58 PM

Warning fellow fifth wheel haulers. Last week after having disconnected my shore power and having connected my kingpin to bed hitch. I reached into the opening behind the kingpin where i had previously neatly rolled and stored my trailer pigtail along with the plastic coated break away lanyard. That's when Sparks flew!! Fortunately my hand was not near the plug end but further down the cable. I can only imagine what would of happened had I have had my hand on the plug. Apparently the seven wire female end of plug came in contact with the bare bolts holding the kingpin and brace support inside. I have always used this area, as I've seen others do to store the pigtail and lanyard. I now have a "Plug saver" on this pigtail and would highly recommend others consider doing so as well. I am curious has anyone else ever experience a similar experience?

twinboat · 01-19-2018, 09:09 PM

One of the pins in the plug is the charge line and connects to the battery.
It should be fused or have a circuit breaker near the battery. If its fused, it may have blown and you may want to check for that.

Gregg121 · 01-19-2018, 09:32 PM

Thanks. Everything inside and out, including lights when hooked to truck seem to be working. Is there one particular circuit I should look for? I thought for sure something wouldn't be working afterwards.

twinboat · 01-19-2018, 10:05 PM

Check the connector, with a volt meter, for power at the blade #4. That is the charge line.

lynnmor · 01-20-2018, 03:08 AM

What do you imagine what would have happened? It’s only 12 volts and will not shock you. Of course flying sparks could cause an eye injury.

twinboat · 01-20-2018, 03:19 AM

Its not the electricity that hurts you, its the reaction to the sparks that causes you injury.

I shorted out 480 volts once, while kneeling. Boy did my butt hurt when I landed.

Gregg121 · 01-20-2018, 07:54 AM

Thanks twinboat, I will test that today and thanks for attaching the diagram .

Gregg121 · 01-20-2018, 12:49 PM

Twinboat, Just checked #4 as suggested reads 12.92 so assume I'm okay? Thanks for your advise.

R2millers · 01-24-2018, 12:18 PM

I think it's a good reminder that when putting the cord back, as most of us do, tuck it back into the kingpin opening, keeping the plug out and feeding it in after the cord is secured. As noted above, no real danger with 12v but it could be a pain tracing back an "open."

Since it sparked and shorted out the #4 terminal, I'd check the fuse box first, but Since you still have 12v at the terminal, apparently it didn't flip the breaker.
Most important, always make sure the brake controller and brakes operate properly. If trailer lights work, you should be okay.

On that note, I know many pull there brake emergency insert while camping to avoid possible theft? Doing that with the power switch on, energizes the brakes and the current flow/ leakage can burn out that switch. I remove my emergency cord when in storage, pulling it out once I've turned off my power switch.

Reverse the procedure when hooking up. Hopefully most have a power switch off the batteries and if not, I'd always install one. I'd also check, just to be sure with a vom, to ensure the power switch disables that breakaway switch.

Here's two good reference pages to sharpen up on 12v electrics.

The 12volt Side of Life (Part 1)

NFlcamper · 01-27-2018, 07:34 AM

The 7 way plug is usually plastic and the contacts are recessed inside the housing. Very difficult to make contact with anything as it is designed to make contact when inserted into a female housing and has tabs to make sure of polarity.

Makes me wonder if the OP has a generator that may have been on and the shore power cord may have fed back and arched. Those prongs can spark if back fed. Should be a switch, either manual or automatic, but things fail.

If it were the 7 way, it would have been the house battery providing the power for the spark. Check the cable for cuts and frays or scrape marks on 7 way plug exposing the metal contacts. If the plug were dragged, the metal contacts could be exposed. Otherwise, contacts should be recessed and protected from making contact with anything.

Gregg121 · 01-28-2018, 06:29 AM

Thank you NFIcamper. No power either shore or generator hooked up. Power came from trailer batteries through the number four hot wire. I'm convinced Twinboat got it right. Though the metal connectors are slightly recessed they still will make contact with the extended bolts inside the housing of the kingpin if lined up just right. The "Plug saver" cap has resolved any future problems.

YC1 · 01-28-2018, 08:56 AM

Is that pin hot all the time? Or is it hot with the truck engine running?

In either case, as mentioned it should have a fuse or circuit breaker. Twelve volts won't bite you but it has a tremendous potential to cause sparks and melt wires. Again, fuses and breakers to the rescue here.

IF that plug is hot all the time and you leave it plugged in to the rv while it is on shoreline your truck battery will be charged up nicely.

twinboat · 01-28-2018, 10:37 AM

Quote:

Originally Posted by YC1

Is that pin hot all the time? Or is it hot with the truck engine running?

In either case, as mentioned it should have a fuse or circuit breaker. Twelve volts won't bite you but it has a tremendous potential to cause sparks and melt wires. Again, fuses and breakers to the rescue here.

IF that plug is hot all the time and you leave it plugged in to the rv while it is on shoreline your truck battery will be charged up nicely.

It is the cord FROM the trailer.