I posted this in the Electrical section as well but I always seem to get more responses from my brothers here..

Have had this vehicle since 05 and been towing since 06, no problems until yesterday when getting the trailer out of storage. In the off season (Northern Indiana) I have an extra brake turn signal light insert for the hitch for added safety. This light utilizes the 4 pin trailer connector just under the factory 7 pin. Plug in the pigtail from the trailer to the 7 pin on the truck and nothing. Have not done any repairs or had any issues with the vehicle indicating an electrical problem. Brake controller is connected to the factory harness and has power.

Attempting some quick trouble shooting before it became to dark I used the 15A blade fuse to light the trailer from the pigtail (campers may know what I am saying, using the 15A fuse in the pigtail will power the trailer lights instead of having to hang extra "pretty" lights for the wife). I then plugged the extra receiver light into the 4 pin, brake light works and flash's with the L&R turn signal as it should. I left this connected and plugged in the 7 pin pigtail to the truck, when i did this the auxiliary light lit up as if the brakes were active but the trailer still was not receiving power.

I am curious if there may be any known or common areas to look for frayed or damaged wires en rout from the front to the back or if the possibility of a blown fuse exists. I am presuming that the factory assembly of the 7 pin/4 pin combo is all powered from the same wiring.

Not the best with electric but not an idiot either, just looking for a little friendly advise/suggestions prior to digging into this issue.

Any questions to clarify anything please feel free to ask..

Thanks gang.

 

Not sure what year you have - but my 03 has several fuses for the trailer connector.
Fuse 6 = trailer tow/stop/turn relay
Fuse 38 = trailer tow park lights and backup lights
Fuse 101 = electric brake
Fuse 115 = trailer tow battery charge
Relay 305 = trailer tow battery charge relay

I'd start with those - test each side of the fuse or just replace them to make sure you're getting a good connection. A trailer wiring tester can help but you can use a multimeter. Unless it was in an accident which could have damaged the wires there aren't really any other specific trouble areas.

 

2003 Limited, Thank you sir I will check those out...

 

No accidents either. Just strange that when I unhooked the trailer back in October it worked fine, no trailer use at all throughout the winter so I doubt I flipped up the door on the receiver until yesterday... friggen gremlins..

I'll have more time to check into this further tonight...

 

I was told on this very forum a year or so ago that the 4 pins of the 4 flat connector share the respective wires as the 7 pin round connector and they just Y off right there at the connectors. I therefore don't think it could be your fuses, if the features that are not working on the 7 pin connector are working on the 4 pin connector. Did you verify with a multimeter that you 7 pin connector is actually not providing power? Its more likely that after sitting in storage, you have corrosion on your connector pins or trailer plug, or you have corrosion somewhere else, perhaps a bad ground on your trailer. Verify that the pins aren't working on the plug with a multimeter before proceeding further with troubleshooting. Clean them with contact cleaner and apply dielectric grease.

 

Great suggestion, thank you. sometimes I cant see the forest for the tree's..

 

I agree (in WI) almost every year we have to replace the 4 pin's on our trucks because of winter corrosion. The best thing I found is in the fall when done using trailers and such fill the 4 pin with grease and spray down the inside of the 7 pin with chain lube.

I believe there is another electrical connection between the 7 pin and the truck harness on the frame not far from the 7 pin. Should be ok since it is a weather pack connector but you never know. Test lights are the best thing for trouble shooting tail light problems.

 

Well, have done some trouble shooting tonight and I believe the Ex is fine. I have a 7 pin to 4 pin adapter and my auxiliary lite works as it should when connected to the 7 pin adapter or to the factory 4 pin..

Time to look for poor ground or worn/corroded pigtail on the trailer..

 

Pigtail it is. The contacts in the pigtail had some corrosion on them but the big issue was the contacts do not have much tension left in them to make a solid connection with the pins on the truck. Cleaned and gently bent back together... all good for now.

Will be changing the pigtail on the trailer before the first trip. Thanks for the suggestions guys, Nice to know the factory tow package is not the issue.

 

Yep that is a problem with that style connector. I used this exact connector and I have had zero problems since installing it. Like I said, when you replace it, smear some dielectric grease on the contacts. And then smear some on it every few months. When you unplug for the winter, put dielectric grease on both the truck contacts and the trailer contacts as part of your winterizing routine. You probably won't ever have to replace the connector again.
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If your trailer doesn't already have one, adding one of this will make trouble shooting WAY easier. Use ring terminal on your wires, not spades. Spades can vibrate loose.
If you end up with a short or a wiring issue you can easily localize the problem, pull the wire and/or repair, and keep going. And if youre an idiot and you forget to plug in your 7 pin plug and it drags the highway for 100 miles until its just a stub, you can buy one from the closest hardware store and wire it in in about 5 minutes. Also makes it way easier to T off your lines to add your breakaway hardware and any other auxiliaries you want to add on the trailer tongue.

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Thank you sir, just ordered...