Trailer Plug Short Circuit Advice?

[garyk]

On our 2002 Ford Explorer, we have both the 4-Flat and 5-Round trailer light sockets.

The 4-flat works perfectly.

However plugging any trailer lights (from any trailer) into the 5-Round socket will immediately cause the, under-the-hood, #13, 30amp, fuse to blow.

Leading me to believe there’s a direct short circuit.

Before I dig into it, does anyone have any advice as to what the problem is likely to be, or tips on troubleshooting it?

[sturgn]

Do you have electric trailer brakes? is so thats where I would start.

[garyk]

Nope, no electric brakes.

[Kirt]

Sounds like your typical ground out. Not much more you can do then trace the wires and find were it is grounding out.

[Kirt]

Another thought... Do the two different plug types work on the same wire system on the ford? If not, I'd say that the program is with the Ford wiring, not the trailer.

[Boatdog]

It sounds like a 12vdc signal in the truck plug is being directly connected to a ground in the trailer plug. Since it is happening on all the different trailers, I would make sure the pins in the truck side plug are in the proper positions. Check the trailer side pin ground position and check the truck side pin ground position. You may have to reposition all of the connectors (or re-wire the plug )on the truck side. Do you know how to use a multi-meter? I can help if needed.

[garyk]

I like that tip Boatdog, sounds about right because that 30A fuse is blowing immediately.

I do have a multimeter.

Sitting here at the desk thinking....

........on the truck side of the 5-round plug, if I couldn't trace the wires to find ground, what's the proper way to identify the ground wire using a multi-meter?

BTW, the 5-round was installed by a shop so we assumed it wsa done correctly.

[Boatdog]

2 ways I can think of:

1. is process of elimination. turn on tailights & emergency flashers. check for voltage in the plug. no voltage on a terminal is probably ground.


2. set the meter to ohms (upside-down horseshoe symbol), De-energize the circuit. Connect one lead to carbody ground or batt negative, and the other side to the plug terminals, one at a time. when the meter reads something like 1 ohm or less, you found it.

[garyk]

Thanks Boatdog, it was that second option using ohms that I was really wondering how to do. Will try it in the daylight. Thanks again.

[Boatdog]

garyk,

Did you find the problem? Inquiring minds want to know...
(my guess is the truck side of the plug has the wires in the wrong positions in the plug)

[garyk]

Boatdog,

I believe there were/are multiple problems.

I did just determine that there is no direct short.

I used your advice to map the wiring of the plugs and receptacles and they all seem to match up correctly.

It looks like there may loose wire splices from where they spliced-in this 5-round receptacle into the original wiring; plus faulty connectivity between the plug and the receptacle on the vehicle.

Now that I have the circuits mapped, I'm gonna start from scratch and install a new receptacle.

BTW, currently the splices into the Fords wiring were done using those blue-colored, pinch on connectors. What do you like to use for trouble-free splices?

Thanks!

gk

[Boatdog]

For trouble free wiring, I offer the following...

I have done it two ways.

1. Slip a piece of shrink wrap on the wire, then crimp together with a non-insulated butt-connector, then solder the wires in the butt-connector, and cover with the shrink wrap.

2. Do an inline twist with the bare wires (so they're straight), solder, and cover with liquid rubber (rope whipping).

[STGRule]

Having spent way too much time on trailer wiring at work, I can agree completely with Boatdog. There is the fast way and the right way. Choose the right way.