4 Way Flat Trailer Connector

[River Hill]

I use a 4 way Flat Trailer Connector on my trailer. The left hand side has stopped blinking. All the wires and bulb look ok. I think the problem might be from my truck. Does anyone know what each of the 4 pins control. I took a test light to them and only 1 blinks with hazards on and only 1 shows a steady light???? I am lost. Maybe it is my trailer.

[Eric ELM]

1 is left turn signal, 1 is the right turn signal, 1 is the tail lights, and the last one is the ground.

Sounds like it is in the truck wiring if it don't light up the tester.

[75]

Brians - here's the standard colour code for trailer wiring:

Green - right side turn/brake light
Yellow - left side turn/brake light
Brown - tail/side marker lights
White - ground

With hazards & parking lights on, your test light should show the following on the truck's plug: green & yellow pins should be flashing, brown pin should be a steady light. If this isn't the case, find & fix the problem on the truck's wiring first - and make sure that the white wire is connected to a good ground on the truck's frame or body.

If the truck plug checks out OK, the problem is on the trailer. I don't know what style lights you have on your trailer (individual bulbs that twist into bases within the light assembly, or the sealed-beam type that the wiring harness plugs into the back of) but check the connections for corrosion buildup - this can prevent the circuit from being completed, even though the wiring is OK. If you have lights which take individual bulbs, double check the bulbs if all the wiring still seems OK - once in a while I have seen a bulb that looked alright at a glance but wasn't working.

Hope this helps - good luck sourcing down the problem.

[earth works inc.]

Brians, if the truck is not too old, go out and buy a complete kit to hook into your existing light system. If it still doesnot work, check the wires from the truck for corrosion, cut wires etc etc.

Then once the plugs from your truck works, go to the trailer lights.

You might pay a little more for the kits that are already wired, but they will work if the truck and trailer is right.

[River Hill]

I just tested the truck and the yellow is the problem. I followed it all the way to where the long 4 way connector plugs into the circle receptacle on the truck. I tested there and still nothing on the yellow. I don't where to go from here. Maybe a fuse?????????????? I would buy one of those kits but the problem is even before where the kit plugs in. Any more suggestions? Thank you guys for your help.

[Eric ELM]

Does the left turn signal work on the truck?

If so, run a wire from there to the plug.

If not, keep tracing farther.

[River Hill]

Thanks for the help guys. I will trace until I find the broken link. I will keep you guys updated.

[River Hill]

I traced it back to a fuse in the power distribution box. On my F150 there are seperate fuses for the towing harness. Thanks again for your help. I guess I will be going Bass Fishing today after all. We have had great weather here in the Mid-Atlantic so I am all caught up, now if I can just get those Bass on my line.

[75]

Brians - that's good news! Glad to hear you're "functional" again. Look out fish! :eek:

Just wondering how well the flat 4-wire plugs hold up for you - if they work fine no reason to change. In my case, I have found that here in Ontario, they l-o-v-e to salt the roads so in spring, these connectors tend to turn green & crumbly. So I switched to a smaller version (mine is 6-pin, but they are also available in 4-pin) of the plug used on tractor/trailer hookups. They have a spring-loaded cover to keep the elements out. Also, I use a plug on the truck AND trailer, so whenever the trailer is parked there isn't a cord end hanging out in the open. Just gotta make sure the "pigtail" doesn't get misplaced...............

[dan deutekom]

Love that pigtail idea. I don't know how many times I have had to replace the plug because it got in the way when backing the truck up to the trailer and pinching it or it fell off the tongue and into the mud. Next time I need to fix it I will make one up like that. Still find that the salt gets into those fancy plugs during the winter.

[CT18fireman]

IN the fall I load the sockets (I use the 7 blade rv style in a plastic socket) up with Di-electric on both the plug side and inside where the wires attach. In the spring I clean out the socket with a degreaser and then reapply a thin coat of grease. I find this helps them hold up even with the sanders slinging sand and salt a them.

[75]

CT18's right - put the dielectric grease to them, and also make sure that where your wiring comes out of the socket assembly is sealed up good too. Some socket assemblies have a rubber boot available to seal the back side up, if not just use RTV silicone and seal things up good.