Truck and Trailer Wiring

(jinxton) · (jinxton) **Join Date: Mar 2002** 03-28-2006, 1:17 PM

I have a 2004 Dodge 1500 and I noticed yesterday when I was loading the boat on the trailer that the rear right trailer lights weren't working.

Through the process of deduction I have figured out that this is a problem in the truck. When I turn on the truck lights the trailer light comes on. When I apply the brake or turn signal the light won't work. The light on the left side of the trailer is fine.
I looked under the truck and all the wires are bundled together. Any idea where to start?
Thanks
Scott

(zo1) · (zo1) **Join Date: Aug 2002** 03-28-2006, 1:29 PM

Just curious...

How are you sure that it is the truck at this point. Have you done more testing than what you mentioned above?

First thing that I would do is get a voltmeter onto the pins in the wire harness that coorespond to the turn signal and brake. Have someone hit the TS and brake and be sure that you are getting power to the adapter.

Good luck, electrical problems can be easy since process of elimination can narrow it down quickly. on the other hand an obscure ground somewhere can drive you friggin batty.

(jinxton) · (jinxton) **Join Date: Mar 2002** 03-28-2006, 1:39 PM

I hooked up my dirtbike trailer and have the same problem.
It happens when I plug into the 4 flat and also when I plug into the 7 round that has an adapter to a 5 flat plug. Both of these are installed from the factory. I did this on both trailers and have the same problem on each of them.

(hemihauler) · (hemihauler) **Join Date: Jan 2006** 03-28-2006, 1:40 PM

Did you try the left light on the right side?

(jinxton) · (jinxton) **Join Date: Mar 2002** 03-28-2006, 1:41 PM

Yes, switched them both and no luck

(hemihauler) · (hemihauler) **Join Date: Jan 2006** 03-28-2006, 1:42 PM

Did you try the left light on the right side?

(hemihauler) · (hemihauler) **Join Date: Jan 2006** 03-28-2006, 1:43 PM

Sorry Double Post

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 03-28-2006, 2:00 PM

I experienced what Manzo talked abtou a bad ground , I never could isolate it....I spent hours tryign ot find it but no luck. I had a similar problem to wha tyour describing. I ended up redoing hte whole trailer. IT was an older MC trailer , single axel so didn't take to long.

(jeffr) · (jeffr) **Join Date: May 2002** 03-28-2006, 2:04 PM

I will assume all your truck lights are all working correctly. Check your fuses.
Get a volt meter and check both the 4 pin and the 7 pin round adaptor for signal. Lights, Turn, Brake, and Back-up. You may also want to check the connections inside your 7 pin to see if anything is corroded or loose. Check the ground wire on your trailer too. If your other trailer is doing it too… probably not a bulb… but worth a shot to try a new one.

Try cleaning off the connections for the wire harness too.

bocephus 03-28-2006, 2:07 PM

I have the same problem with my '02 Dodge 1500. The drivers side tail light will not work on the trailer but works on the truck fine. When I tow with one of my other trucks the lights work fine. Every trailer that I tow with the '02 Dodge 1500 doesn't light up. It's somewhere in the dodge wiring for me. The break light on the truck has burnt out three times in the last three years while I haven't had one light blow anywhere else. Fun, Fun!

(jinxton) · (jinxton) **Join Date: Mar 2002** 03-28-2006, 2:39 PM

My drivers side brake light has been burned out for quit some time - yes I've been to lazy to fix it, but have not had a problem with either trailer till now. I'm off to buy a new bulb and see if that helps.
Bocephus, my light blew in the first 6 months, what's up with that!!!!

(spoonman) · (spoonman) **Join Date: Aug 2005** 03-28-2006, 4:28 PM

right and left signal/brake lights fused seperatly
fuse no. 47 under hood is for right turn/stop at trailer plug.

(jinxton) · (jinxton) **Join Date: Mar 2002** 03-28-2006, 6:42 PM

Brad
You da man!!!!!!!!!!!!
That's exactly what was wrong. Gotta love this board for all the info that is available.

(spoonman) · (spoonman) **Join Date: Aug 2005** 03-29-2006, 6:03 AM

Glad I could help. I'm a lead tech at a chrysler/ford dealer if ya need any thing else...

check to be sure that nothing is shorted on the trailer more than likely this is what blew the fuse prolly when ya backed in the water.

(carcrz) · (carcrz) **Join Date: Mar 2006** 03-30-2006, 3:24 PM

I have an '05 Ram 2500. SAME STINKING PROBLEM!!!