funky dodge ram trailer wiring

[Ciera2450]

Hello to everyone! I have a restore/refurb thread going but thought I'd post this question here. I have a 2004 Dodge ram 1500 with four flat trailer harness connection. The left trailer turn signal and brake light quit working. I went through all of the trailer wiring and it is NOT the trailer. Testing the harness on the truck end shows NO voltage on the yellow (left turn) wire when the signal is applied. The right side shows a pulsing 13.7 or so volts when applied. So, I checked the fuse in the engine compartment and all fuses are good. I even replaced them just for the heck of it and still nothing. Testing the fuse slot DOES show voltage for the left trailer lamp fuse. I can here a tick (relay?) when the turn signals are on coming from the fuse block somewhere but there are NO relays labeled for trailer wiring or turn signals. I believe the trucks turn signal relays are in the cab....
I dunno if it matters...but I do notice a VERY slight difference between the left and right turn signal "tick" in the engine bay. But when either turn signal is applied there is a relay sounding tick tock.
I suppose there could be a short in the wire somewhere but its all secured up in the factory wire loom. I'd hate to tear it all out if thats not it....

Any trailer gurus out there that can help me diagnose this????
Thanks guys!

 

[Ciera2450]

Re: funky dodge ram trailer wiring

I do have left side trailer running lights...

 

[UncleWillie]

Re: funky dodge ram trailer wiring

Is this factory tow wiring, or aftermarket?

What are the results if you turn on the 4Way/Emerg. Flashers?

 

[Scott Danforth]

Re: funky dodge ram trailer wiring

if its a hopkins harness, there is a diode module that is behind the left turn signal. these have gone bad on me in the past.

running lights are a different wire than the brake light/turn signal.

 

[sschefer]

Re: funky dodge ram trailer wiring

If the turn signals on the truck work I'm not sure why you would question fuses. If you have a third brake light you would have the diode but if 3rd brake lamp(s) light when the brakes are applied and doesn't blink when the signals are used then it's fine. Check up under the rear bumper and make sure the connector to the receptical isn't damage or badly corroded. If it was a back yard install they might have used vampire taps to tie into the lights. It's a pretty common method and works great if they're wrapped in tape. They'll corrode after a couple of years if they're left exposed.

 

[Ciera2450]

Re: funky dodge ram trailer wiring

It is the factory wiring. I'm not sure what a hopkins harness is...so i don't have one??? Lol

As I said I can hear what i think is a relay near the engine compartments fuse box when the turn signal is applied. I can also here(and find it!) one under the dash in the truck. They could be the same click and i'm just hearing things because I can't for the life of me find the relay that I think i'm hearing. It sounds like its coming from "inside" the fuse box. The label shows a bunch of relays but NONE for turn signals. I've even pulled out all of the relays one by one and its not any of them.
I find it hard to believe its a shorted wire somewhere.
There is a connecting harness for the factory wire bundle that runs rearward behind the drivers side wheel well and I plan to see if i've got voltage on the yellow wire there... If so...its gotta be a short from the harness to the rear of the truck. Everything else works in the harness...tail lights on the truck and every other trailer wire.

Scott where is this diode you speak of?

I've got to be missing something....
Thanks for the replies guys!

 

[Ciera2450]

Re: funky dodge ram trailer wiring

sscheffer, it is the factory wiring and runs in the factory wire loom. It does NOT jump of off the trucks lights. There are seperate fuses for the trailer signal and brake lights and truck lights. I did check for corrosion and I even hard spliced the wires together, bypassing any harnesses....NO luck. I'm confused...Thanks for the help!

 

[Ciera2450]

Re: funky dodge ram trailer wiring

I haven't checked the third brake light...I never thought anything about that in fact. I'll run out and see if it works.
(Checked it, third brake light on the truck works fine)

 

[Scott Danforth]

Re: funky dodge ram trailer wiring

what you hear is the turn signal flasher. it should be behind the left kick panel if I recall correctly.

are you sure its a factory harness. most trailer wiring is a dealer added feature. they are a plug-n-play accessory.

the diode pack is part of the wiring if you have a hopkins harness. (common brand of aftermarket harnesses). the harness plugs into the factory harness between the truck harness and the rear lamp assembly. pull the two screws, remove the light assembly. there should be a t-harness connector. if 6" from that T-harness connector is a small black box about 1" x 2" x 1/2", that would be the diode pack.

 

[Josh P]

Re: funky dodge ram trailer wiring

2004 rams had a problem withe the fuse box going bad, the trailer turn signal relay is internal to the front fuse box and not serviceable, also very weak from the factory,(common problem) its about 400 for a new one from a dealer, the replacments are slighty more heavy duty but the relays still are not servicable

 

[Ciera2450]

Re: funky dodge ram trailer wiring

Thanks for the help scott,
I have pretty much traced the wires from the trailer harness to the front of the truck. Everything is in what appears to be factory wire loom, the trucks light wires run in the same harness and there are no breaks in the wire loom. The wires from the truck lights and the trailer harness enter the wire loom at the same point but they are not spliced anywhere. There are seperate wires for each.

 

[Ciera2450]

Re: funky dodge ram trailer wiring

Josh P, Thank you! I knew I wasn't hearing things!!! lol
Crappy news its 400 bucks tho! To fix the dang trailer turn signal...

Its completely not servicable? I've got a buddy who's pretty good with electronics.

 

[Josh P]

Re: funky dodge ram trailer wiring

there has been people who have taken them apart and soldered leads to add external relays... its worth a shot.. , let me get you some diagrams you can verify that there is no voltage outta the box, you have checked your fuse already for the trailer?

 

[Ciera2450]

Re: funky dodge ram trailer wiring

Yes sir, I even replaced it just for good measure. I've got voltage at the fuse. As I described earlier, when the Left signal is turned on the relay "click" sounds slightly different than the right ( the working light). I'm betting its that internal relay that has gone bad.
The diagrams would be awesome! Thanks again..

 

[sschefer]

Re: funky dodge ram trailer wiring

sscheffer, it is the factory wiring and runs in the factory wire loom. It does NOT jump of off the trucks lights. There are seperate fuses for the trailer signal and brake lights and truck lights. I did check for corrosion and I even hard spliced the wires together, bypassing any harnesses....NO luck. I'm confused...Thanks for the help!

Got it. If the fuse isn't blown it's open not shorted. Do you have an automotive probe style tester. The ones with the sharp point, a ground clip and a light in the handle. You could work your way down the harness until your find where that rock that flew off your tire hit the harness and cut the wire. Just speculation.. Seen it happen a few times.

 

[Josh P]

Re: funky dodge ram trailer wiring

Yes sir, I even replaced it just for good measure. I've got voltage at the fuse. As I described earlier, when the Left signal is turned on the relay "click" sounds slightly different than the right ( the working light). I'm betting its that internal relay that has gone bad.
The diagrams would be awesome! Thanks again..

pm with your email i will attach a copy of the wiring diagram from mitchells

 

[Josh P]

Re: funky dodge ram trailer wiring

ok sent, you may be able to pick a used one up for about $100 use that one and give your friend the broke one to see if he can fix it

 

[Ciera2450]

Re: funky dodge ram trailer wiring

Is there any reason I can't tap into the truck turn signal wire (at the tail lamp or at the fuse box) for the left side trailer turn signal?

 

[Josh P]

Re: funky dodge ram trailer wiring

on the rams the turn signal and brake lights are two differnt bulbs and on your trailer it is one... so no, unless you buy a converter.

http://www.etrailer.com/Custom-Fit-...ckup/2004/119175KIT.html?vehicleid=2004300232

 

[UncleWillie]

Re: funky dodge ram trailer wiring

ok sent, you may be able to pick a used one up for about $100 use that one and give your friend the broke one to see if he can fix it

Or, Just pretend the factory wire harness was never installed, and install an aftermarket tow wiring harness for $35 Here.


Edit: Josh beat me to the send button by a few seconds!