Trailer lights: Left signal and left brake light don't come on. All else OK

[gt2003]

That pretty much sums up my problem. It was all working fine last time we hooked it up, now this. It does the same thing when I plug it straight in from the 4-pin as it does when I use the 7-pin adapter. There is a ground wire towards the rear of the trailer but it's going into rust metal. BUT, my non-electrical mind doesn't "see" how this could be the issue if the running lights are working. So, set me straight. Thanks

 

[GA_Boater]

Fix the grounds. To make it fool-proof, run a ground to each light.

For your non-electrical mind, rust doesn't conduct electricity well. And most trailer light problems are some lights work and some don't. It's magic. LOL And 99% of the time it's a ground issue.

 

[MTboatguy]

Your grounds are bad, clean the rust and apply some dielectric grease put back together and see what you have.

 

[oldjeep]

Left signal and left brake are same wire. Trace it back. If you have running lights at the left taillight then it isnt a ground issue.

 

[GA_Boater]

Forgot one other thing - Swap bulbs left to right, could be a blown bulb. And fix the ground.

 

[blamtro]

Friend had same issue. Check the pin on the receptacle on the tow vechicle isnt bent out of the way. In my friends case, just had to bend it back so the pigtail made contact. This left stop/turn is a separate circuit from running lights.

 

[gt2003]

I did some testing for what it's worth. I seem to get full reading on the brown wire and get a very minimal "bump, bump, bump" on the yellow wire. I've cleaned up the front and back ground wires. There is still one more ground that's been installed by the marker lights. I'm going to clean it up after work and see if that could be the issue>

oldjeep since I'm getting the small turn signal bump on my meter, could it still be a ground or should I be looking somewhere else?

Would there be a fuse for just the left turn signal/brake? I can check out the manual today

 

[gt2003]

Oh, light is good. Picked up a new one and am using that. I've still got the old one as well if needed

 

[oldjeep]

I did some testing for what it's worth. I seem to get full reading on the brown wire and get a very minimal "bump, bump, bump" on the yellow wire. I've cleaned up the front and back ground wires. There is still one more ground that's been installed by the marker lights. I'm going to clean it up after work and see if that could be the issue>

oldjeep since I'm getting the small turn signal bump on my meter, could it still be a ground or should I be looking somewhere else?

Would there be a fuse for just the left turn signal/brake? I can check out the manual today

Once again, not a ground if your left running light works. Issue with yellow wire somwhere in circuit. Start by verifying signal from truck is good, then work your way back. Could be corroded connection or just a mostly broken wire.

 

[gt2003]

Replaced the entire 4 way flat wiring harness and all is good now! Thanks for your help folks!