Tow Vehicle Trailer Light Help Needed

[reelcharacter]

Greetings,

First post from this electrically un-inclined 2003 Tundra owner.

I have a new dump trailer that I occasionally tow. All lights work fine on the Tundra with and without the trailer connected. When the trailer is connected 4-way flashers (and ea side signal lights) work. Brake lights work. Running lights and back up lights do not work.

I connected the Tundra to another trailer with the same results. So through my amature diagnosis, I have determined the problem rests with the truck and not the trailer.

Then I followed some advice and spliced a wire to the white ground just ahead (truck side) of the 7-way trailer connector. With the ground end firmly threaded between the threads of a bolt tightened into the metal bumper frame I still have no lighting change.

Now for the questions:

1. Is there still a possibility the ground could be the issue? If so, where is the truck side trailer wire harness grounded? What else is there I should do with the tow side ground?

2. Is there a fuse on the truck side that could be the problem for the lights that do not work yet not the lights that are working?

3. Is it time for a new OEM/aftermarket truck side connector? I have considered a combination 7-way and 4-way (side by side) connector since I also have a small utility with the u-haul style 4-way connector.

Have I left anything out? Oh yes, LOVE THE TUNDRA !!!

Thank you in advance. Your suggestions are appreciated.

Sincerely,
- Reelcharacter

[Codiac]

Just want to be clear of what is or is not working. You are saying that when hooked to the trailer the marker and backup lights don't work on the truck....is the correct?? Are the markers and backup lights working on the truck when not hooked to the trailer???? Are the markers working on the trailer when hooked up?? There are no backup lights on the trailer so we don't have to worry about that.

[kwarstler]

First I would check the filaments in the bulbs. Make sure they are all intact. If the bulbs are intact, I would suspect the circuit is not completing itself for the running and backup lights. I would further suspect the short is in the trailer wiring itself. First off, I would try to plug it up to another person's truck to see if it works. If it doesn't, then it most certainly is the trailer wiring. If its the wiring, you can try to sort out the wires and replace, or simply buy a new set of trailer lights - (you can get the new cooler and brighter LED lights then!) I realize this isn't a whole lot of help, but it's a start to at least look into.

[reelcharacter]

Thank you for the replies, I will try to answer them both. I did hook the truck up to another trailer and the marker lights did not work on the other trailer, just like they did not work on my trailer. So by this I concluded the problem is in my truck. (All other lights work fine on the trailer and truck). The trailer was brand new in 2007 and is set up with LED lights.

Thanks in advance for your help!
-reelcharacter

[Codiac]

You are setting the trailer onto the hitch ball right?? Many trailers ground thru the hitch ball. Sounds like a wiring issue and might be something as simple as a wire not connected correctly in the plug.

[jpnca]

Use an ohm meter and make sure the circut is complete or at least goes where you want. Double check your grounds

[07tundra@10k]

Not all trucks and trailers are wired the same!!! Toyota Uses thier own wiring arrangement in the plugs. If I go to use my buddies trailer I have to use an adapter to make the wires right. You might check with NAPA as they have 7 pin dodge, 7 pin GM... I actually use a Dodge adapter for one of my trailers. It saves the aggravation of trying to switch the wires for each trailer you are using.