I have a 1995 Toyota Tacoma. I was towing with the same truck and trailer all season long, when, all of a sudden, the trailer running lights stopped working. I got out my test light and discovered the running lights on the wiring harness worked before the black converter box, but not after. I bought a new towing harness for the truck (From NAPA; Plugs into the rear lights.; It has a black converter box; 4 prong plug) thinking this would fix the problem; however, the same problem exists. The running lights on the wiring harness work before the black converter box, but not after. Thinking the harness may not have been well-grounded on the truck, I grounded it directly to the truck battery using jumper cables, same problem. Everything works on the trailer except the running lights. The trailer works fine on another truck, so I know it is not a problem with the trailer. Also, all of my Tacoma lights are working fine. I am baffled... Thank you in advance for your assistance!

 

do you have the part number to the converter box your using by chance?

 

This is the wiring harness I am using: http://www.hopkinstowingsolutions.co...100_95-04.html. Thank you in advance!

 

ok so your testing the brown wire right before and right after the little black box? or at the harness ends? Well it should be a plug and play and no splicing, but if not fortunately the running lights dont need any converting ( bulb circuit does not have to be shared for like on the signal/brake light ) you can jump the brown wire from before the black box where you are getting power to after on the brown where you are not getting power (4 pin plug side). Let me know thanks

 

The converter converts it from a 5 wire to a four wire. The truck has separate bulbs for the turn signals and the brake lights...

 

Exactly, what I'm trying to say is you can splice the BROWN wire that goes INTO the converter box around to the side where the BROWN comes OUT to the trailer. This wire simply passes through the box WITHOUT any conversion. (well its supposed to but yours doesn't seem to work) If it were a problem with the signals or the brake lights on where it converts from separate bulbs to a single bulb you could NOT do this. You can do what I mentioned or replace that defective converter box, either should work, however since you had this problem with the first box, I would recommend soldering and heat shrink (or high quality electrical tape) this connection especially since its outside the vehicle

 

Just a quick update...returned the harness and got a new one...I believe it may have been a bad ground and/or bad converter...whatever it was, it now works great. Thank you for your assistance!

 

No problem, anytime man! Nice glad to hear you got it, weird to see 2 bad units though