Trailer light question- both lights blink dimly on left turn, brand new installation.

I just put brand new lights on a trailer using a brand new wiring harness. I used shrink connectors on the splices, matched up the wires, etc. I ground the trailer frame down to bare metal, put the ground on there and then put some caulk over it.

I tested the lights and they almost all work, except when I put on the turn signal for left turn, both lights blink very dimly.

I googled, it says a possible grounding problem, so that is going to be my first step, on the trailer and on the tow vehicle. Is there anything else I should check?

By both lights, do you mean both trailer or left trailer and tow vehicle ?

Grounds of course are the first suspect.

Grounds. . . . . . /thread

If it has bulbs (not LED) check them. Seen this on a few lights, bulb quality isn't what it used to be, especially the bulbs that come with the lights. If they are LED, maybe try a know good light to make sure one isn't defective.

iceracer wrote: By both lights, do you mean both trailer or left trailer and tow vehicle ? Grounds of course are the first suspect.

Both trailer lights, yes. I'll check the grounds.

Are you sure the trailer connector on the tow vehicle is wired correctly?

Grounds....

Check the tow vehicle to trailer grounds...

Clarification: the tow vehicle has been wired for a while and worked on other trailers without issue. The new wiring is on the trailer only. I didn't get a chance to check it today, but I am going to redo the grounds on the trailer and the vehicle.

Start with the ground on the left hand trailer light.

Take jumper cables and connect directly to the truck frame. Then connect as close to the lamp fixture ground as possible. If the lights work, you know it's a ground issue. I settled many parts store arguments by doing this. People said my bulbs didn't work, or my connector had a short in it. 30 seconds and I could prove it was their problem, not mine.

You do have the trailer hitched to the truck, right? Not just connected through the plugs? I had a brain fart, once, and didn't drop the trailer hitch on the ball, and couldn't figure out why the lights were acting goofy, when they've been fine for the last decade. Hitched it up, and lights worked as they should.

RealMiniParker wrote: You do have the trailer hitched to the truck, right? Not just connected through the plugs? I had a brain fart, once, and didn't drop the trailer hitch on the ball, and couldn't figure out why the lights were acting goofy, when they've been fine for the last decade. Hitched it up, and lights worked as they should.

If the truck and trailer are properly wired then you don't need the ground through the trailer hitch.

Some lights are grounded from the bolts to the trailer. Make sure sure the washer/nut surface area is cleaned to bare surface.

The ground problem should be in the left light, it is grounding through the right light. The best thing is to run a full ground through the lights. Second best is to make sure all ground connection are using star washers.

In reply to APEowner:

Fair point. In my defense, I hadn't wired the truck.

RealMiniParker wrote: In reply to APEowner: Fair point. In my defense, I hadn't wired the truck.

Back in the pre-internet days before you could Google "trailer wiring diagram" and learn that there are standards for such a thing I wired up a truck and trailer without a dedicated ground wire. It worked fine...as long as you didn't go over any bumps...or turn.

So, I went outside yesterday evening to mess with this and had seven mosquitoes land on my legs in less than 10 seconds, while a larger cloud of them surrounded me. I retreated back inside.

Before I mess with the trailer again, I'm going to have to trim the higher grass on the edge of the property, eliminate any standing water and set up some decoy nesting areas which will get dumped every couple of days. I may also have to make a few 2 liter soda bottle traps and bust out the fan to disperse them while I am working.

I went out, checked/redid the grounds on the two vehicle and the trailer and re-did the connection for what I thought was the turn signal on the driver's side.

Same problem. I took the light apart and saw that the wire going to the turn signal is brown. I was expecting yellow, based on past experience with what is standard. The passenger side is also brown.

Anyhow, no improvement, but I only spent like 15 minutes on it. I may have to actually take the time with a multimeter to figure this out.

The bulb is probably good the light fixture is not grounding properly. Check continuity from the light socket to the ground wire on the plug sounds like a break in the circut somewhere. New light fixtures sometimes have faulty wiring.

Is it a HF trailer? If so, I think I had to run a dedicated ground to get everything to work properly.

Double check and clean your plugs at the truck. Sounds more like a corroded/collapsed contact in the main plug.

It is a HF unit. I'll mess with it more, thanks for the confirmation that it might just be HF quality and not something I did with the wiring.