[firecat1981]

Been wrestling with an issue and now I'm stumped. My brake lights and turn signals work fine, but the running lights and hazards don't. The side marker lights work fine, but the running lights at the rear of the trailer won't come on, and when I put on my hazards only the left side works.

What I have done to trouble shoot so far:
I checked the wiring harness from the truck all the way back and everything is getting power as it should, and when it should. I cleaned and secured all 3 grounds. Since my truck did not come with a tow package I don't have auxiliary fuses to blow.

So now I'm stumped, my next step is to buy a whole new light kit and replace everything. Thoughts?

 

[Brett]

Did you check the trailer light relay up behind the bumper?
The one on my 2001 Tundra went bad at 125k miles.
Had to install a new one to get everything functioning properly.

 

[firecat1981]

Yep, installed it myself, just checked it a few hours ago with a test light and a test plug. Then worked my way back to the trailer lights, everything is getting power, even tried running an extra ground to the outboard motor. I'm out of ideas.

 

[Brett]

I've been known to clamp a temporary ground wire to the vehicle engine block,
then with the other end of the very long ground wire, check each light fixture
to see if a secondary direct ground solves the problem. If it does, that tells me the
ground between the fixture and trailer frame has corroded and broken the circuit.

 

[firecat1981]

These are the continental white lights that don't really come apart, I'm starting to think the issue is internal corrosion within the fixture themselves. I did clean and tighten the ground wires before running the extra ground to the outboard.

 

[Brett]

Sounds like in wire or terminal corrosion.
Need a volt/ohm meter to check resistance and continuity on each wire.

 

[firecat1981]

Well I wanted to upgrade to LED lights anyway, lol.

 

[firecat1981]

Well those cheap white continental lights that so many swear by turned out to be the culprits. It's funny they both had internal issues in different ways. I was going to rewire the whole trailer, but decided to try the new LED lamps first to see if that was the issue. Since they work perfect now I just cleaned up the wiring and left it as is, if something goes wrong I have a full spare harness to use next time.

On a side note, the LED tail lamps are easily twice as bright as the old incandescent ones.