Trailer Driver Side Brake Light & Turn Signal

2005 TRD Off-Road, all lights working when boat trailer is hooked up EXCEPT driver side turn signal and brake light. This light has power because the bulbs will light up when truck lights are on, but they are not activated by the brake or turn signal. Could this be a fuse problem? Everything on the trailer end seems to be fine, so Im thinking the problem must be on the truck end. Thoughts anyone?

 

Does the Vehicle lights still work ok when the trailer lights do not ??? If so I'd check the trailer wiring for that side and be sure the left signal / brake, parking light and ground are correct for all wires from the trailer connector to the lights. IF these look ok and you have a "converter/isolation module that taps into your vehicle lights and gives out a connector for the trailer - this may be bad as well. They do sell a test plug for only a few dollars that you plug into the vehicle trailer connector and leds will tell you that it's working correctly from the vehicle - this isolates it to either the wiring coming from the vehicle - or if that is ok per the tester - then it's in the trailer. Some testers can but used "in line" with the trailer so you can always be sure .... Again, Check the ground wire the trailer - and the ground connections at the lights .....

Good luck

 

Trailer lights can always be a problem but I think we can get this one working. It should not be a fuse problem because all of the other trailer lights are working. Usually with a fuse problem, no trailer lights will work.

First thing to do is to take the bulb from the passenger side and put it on the driver side. Give the bulb time to cool before touching because they do get hot from being on.

Just because you have running lights on the driver side does not mean the bulb is good. The bulb has two filaments. One for the running light and one for the brake and turn signal light. Hopefully the brake and turn light filament is burned out in the bulb. This would be an easy fix with a new bulb. You could reverse this process with the bulb switch to see if the bulb works on the passenger side correctly.

Ok the bulb is good. Next you will need a test light to check for power. Trailers usually have four wires. (white, yellow, green and brown) White is the ground and will be attached to the frame near the tongue. The brown wire is the running lights for the trailer and should go to both rear lights and any running lights on the sides of the trailer. The green wire is the right side (passenger side) brake and turn light. The yellow wire is the left side (driver side) brake and turn light. The easy way to remember this, is by the letters in the word green and yellow. Green has a (R) for right and yellow has a (L) for left.

Check the yellow wire where it comes to the back of the driver side trailer light. Turn on your vehicle running lights and driver side turn signal. Use the brown wire to make sure your test light has a good ground to the trail and is working correctly. Your test light should stay on when pushing into the brown wire. When pushing the test light into the wire, make sure not to touch the trailer frame. Now push into the yellow wire and the test light should blink. Blinking mean you have power to this point in the wire. Blinking test light, you may have a bad light housing, bad light housing connection, or the bulb seat connection needs to be clean. Make sure the yellow wire is connected to the housing or the wire is not broken at the housing. Sometimes the wires will pull out of the back of the light housing. Turn off the vehicle running lights and turn signal. If the wire are good into the housing, use a flat tip screw driver and sand paper to clean the terminal where the bulb going in the housing. Make sure to turn off all your vehicle lights before doing this.

Now if this is not the problem, you will have to start at the vehicle and work back down the yellow wire to the light. Check for power of the plug at the bumper. Sometime the flat plug containing all the wires from the trailer will have a broken wire. This can happen just from plugging and unplugging the wires over time.
You can see which of the plug wires is the yellow one here. It should be the middle female from the vehicle and middle male from the trailer plug. Use your test light to test for power at this connection also. Sometimes this connection needs to be cleaned too.

Hope this helps.

 

Thanks for the detailed responses. Spent a while on it yesterday and got it figured out. The yellow wire was damaged toward the back of the trailer. Unfortunately for this model of trailer (trailstar for 2001 bass tracker), I had to buy the entire wire harness. Luckily only $40. Thanks for all the help.