Trailer light plug problem on the car end

[Dr. Arquero]

I found that my trailer left brake light and left turn indicator weren't working. After rewiring the trailer with a new plug and wires, it still didn't work. So I switched the right and left wires and whwn the left worked and the right didn't I figured out that the problem was the car, not the trailer wires. For whatever reason, only the left brake and turn indicator aren't working, where they worked fine last summer. I tow it with a 2006 Toyota Highlander. The connection is a 4 flat connector - nothing visibly wrong with it. I checked the highlander's fuses and I can't find anything that would explain a failure on one side. Maybe I'm missing something. Is this a common problem. Anyone heard of this? Any suggestions?

 

[wrench 3]

Is it a factory installed connector or was it added on?

 

[Dr. Arquero]

It's the 4 flat connector that came with the care - in a compartment, you leave the wires and plug hanging out the back when in use. I didn't get the "towing package".

 

[wrench 3]

If it doesn't have a towing package, they probably wired it in behind the tail lights. Remove the access panel inside the vehicle behind the left hand tail light and check the splices that were added to the wiring.

 

[fishin98]

It all starts with the ground..I had the same issue....is your trailer a TILT TRAILER?? If so you need to run a jumper ground from the main beam of the trailer to the trailer frame. Also you need clean connections at the vehicle. Most if not all wiring connections in the vehicle are now through a 3 way harness that plugs into the vehicle wiring system at the light harness in the rear.

 

[airshot]

You would be surprised how many trailer light problems come from the tow vehicle. If you have winters to go thru then that car plug gets a lot of abuse. I have saw many people working feverishly rewiring the boat trailer only to find the car plug is the problem. About every three years I just replace both the trailer and car plugs to be safe. I typically find corroded connections in that process so it pays to change them out on occasion and they are very inexpensive to do so.

 

[NYBo]

Welcome to iboats!:welcome:

Chances are there is a converter in the system (converts separate brake and turn signal signals in the Toyota to the combined circuit for the trailer connector). This converter may be the culprit.

 

[Silvertip]

Why not just use a test light on the car end of the system and see what works and what doesn't. If your vehicle has amber turn signals or separate lamps for turn and stop at the rear, you MUST have a converter to make the trailer lights work properly. To isolate trailer problems, use a battery charger and a nail to power each of the three circuits. Connect the negative lead of the charger (or a separate battery) to the trailer frame (make sure this area is not painted). Put a nail in the positive clip and then probe each of the three circuits (left turn, right turn and running). Brake lights are just turning on both left and right turn simultaneously.

 

[Dr. Arquero]

After pulling out all of the trim panels on the back of the Highlander, I realized that ten years ago I had U-Haul put in the wiring with the trailer harness as well as the hitch. (Dohhhh!) There is a trailer light power module that is the most likely culprit. U-Haul says they're good for about ten years and will replace it for $74. Oh, well.

 

[gm280]

After pulling out all of the trim panels on the back of the Highlander, I realized that ten years ago I had U-Haul put in the wiring with the trailer harness as well as the hitch. (Dohhhh!) There is a trailer light power module that is the most likely culprit. U-Haul says they're good for about ten years and will replace it for $74. Oh, well.

I am sure U-Haul would replace it for $75 dollars being how they are usually half that price. Do a little internet search a see.

 

[thumpar]

That price seems pretty high especially since you already have one of their units. They usually run $30-$35. That is not the best way to keep customers.

 

[fishin98]

Go to your local auto parts store, check and see if they have on hand or can order the complete plug in harness. Did that for my 1995,99 and 05 Jeep Grand Cherokee's. Normally they do carry the kits for all popular brands. Plugs right into your light system.

 

[Silvertip]

And before you do that, have you proven that unit is actually bad? Troubleshoot - Troubleshoot - Troubleshoot - then repair.