I'm stumped.......

My left turn signal does not work on my trailer. The tail light works. When I connect the light to a 12 v battery it works just fine both parts of the bulb light up, but when I plug in to my car the tail lights work but not the left turn signal. When I plug in one of those testers to test the output from my car it shows it as working properly. I'm at a loss. Everything seems to be grounded properly. I would imagine if it were not grounded the tail lights would not work. Is that a correct assumption? Any help is appreciated!!

Re: I'm stumped.......

Grounds on trailers, particularly boat trailers, are always a problem. I prefer not to use the chassis of the trailer as a ground, as corrosion seems always to cause problems with the connections to the metal. Particularly on electric trailer brakes, I like to wire in the grounds without using the trailer chassis at all.

That said, I have seen numerous cases where grounds were bad, and one light or the other would work, but not both. To test this out, make yourself a long jumper wire, the length of your trailer, with alligator clips on both ends. It may seem kind of elementary, but remember that you need only +12 volts and ground at each light to make them work.

Clip one end of the jumper wire to the tow vehicle ground (perhaps even to the negative terminal on the vehicle battery), and the other end to the ground of the problem light fixture. Then test the lights and see what works, and what does not. Based on the results, you may be able to come to some conclusions as to where the problem is located.

I also find that the standard, rather simple 12 volt test light is highly useful for trying out trailer light circuits.

Good Luck!

skinorth

Re: I'm stumped.......

One more thing... there is power to the light. I used an Ohm meter and turned the blinker on and it showed power. However, the light will not blink. I even took my right side light that works and put it over on the left side and it did not work. I'm pulling my hair out over this one.

Re: I'm stumped.......

Just a thought here, from personal experience. I drilled holes for a Power Caster adapter for my trailer and inadvertently cut wires in the frame at the tongue and it caused all kinds of weird things, like you mention. I had to repair the wires and got it back to normal.
My Dos Centavos, Ed

Re: I'm stumped.......

Your correct about the ground if the tail lights are working then the ground is good. There is only one ground. The brake and turn are the same, the turn is just an intermittent brake light. Try the brakes, if it lights then you have a problem in your cars turn signal but my guess is that you won't have a left brake either. That being said, you're lucky, there's only one wire to trace out.

Re: I'm stumped.......

Take a look at your tow vehicle owners manual. I had the same exact issue when putting in a new set of trailer lights. It turns out my vehicle had separate trailer fuses for left and right tail lights, left turn signal and right turn signal. These were separate from the vehicle tail fuses. There was no fuse at all in the Drivers side trailer turn signal. Probably pulled at the dealer to make another car go out the door.

Ray

Re: I'm stumped.......

Trailer lights do some really strange things when they have a bad ground. I would not rule that out. How is the bulb holder ???

Re: I'm stumped.......

You have not indicated the style lights, but I must assume they are incandescent bulbs. I agree that the ground sounds good as it is the same for all lights. (I also agree that you should not be using the chassis ground, but a direct connection.)

Having read the other suggestions, and your statements that there is power present at the socket, I would check the bulb. Not to see if it was blown (altho you could verify continuity anyway - not just visual) but to make sure the little blob of solder is making contact with the socket base.

Sometimes the base contact surface can get "stuck" in the brass socket, restricting it's movement, preventing it from touching the bulb base. It is either being pushed against the bulb base by a weak spring, or sometimes a rubber spring. In either case the brass can get a little corrosion inside that interferes.

Another possibility is that the bulb isn't seating correctly, either due to being "cocked" in the socket, or the blob is too small. It is possible that the socket needs to be squeezed tighter (done w/o the bulb inserted) to tighten the brass, allowing the "tits" on the bulb base to properly align in the socket.

I have even had occasion to add a tiny drop of solder to the bulb contact points to improve on their ability to make contact.

Happy hunting.

Re: I'm stumped.......

La Bullet said:

Just a thought here, from personal experience. I drilled holes for a Power Caster adapter for my trailer and inadvertently cut wires in the frame at the tongue and it caused all kinds of weird things, like you mention. I had to repair the wires and got it back to normal.
My Dos Centavos, Ed

Click to expand...

I see from your photo that you have a coupler lock. I would also suggest that you use a latch lock on the lock, not just the clevis pin. It would be awful easy to use a grinder to cut off the coupler lip and drop your lock out of position. I use a similar lock that covers the complete coupler, but it is still pretty loose when the latch is opened, so I use the latch lock to try to slow them down.

And what the heck is that thing behind the jack?

Nice setup by the way.

Re: I'm stumped.......

I had a similar issue on my trailer. In my case, I even hooked up my vehicle to my neighbors boat trailer and the lights worked just fine. I also powered up the individual pins on the trailer end and they worked fine. Plus when I disconnected the trailer, the voltages at the pins were fine. The only time it would not work was when that trailer was plugged into that vehicle. Eventually, I tracked it down to my trailer light converter (the little box in the vehicle end of the harness that combine brake and turn signals into a common filament, if I recall correctly) was borderline. I suspect that his trailer drew just a little less current and the converter box thought that my trailer was shorted and so it shut down to protect itself. In any case, now that I have replaced the box, the lighting works just fine now.

TerryMSU

Re: I'm stumped.......

Terry, I was just about to ask about that. I suspect that is my issue, because everything on my trailer seems to be in working order. I am going to connect to my neighbors truck and make sure it's not the trailer. Thanks!!

Re: I'm stumped.......

It's fixed!!!!! It was the convertor box from my car. It was a very easy fix. I bought a 5 to 4 convertor at Autozone for 13.99. Installed it and everything worked perfectly. Thanks for all the advice!! This is a great forum!!!

Re: I'm stumped.......

Deleted, I see you fixed it.

Re: I'm stumped.......

smann said:

It's fixed!!!!! It was the convertor box from my car. It was a very easy fix. I bought a 5 to 4 convertor at Autozone for 13.99. Installed it and everything worked perfectly. Thanks for all the advice!! This is a great forum!!!

Click to expand...

You are lucky. I had to try three different auto parts stores to find one, and then I had to splice the 4 pin connector on it. This was over Memorial Day weekend, and I wanted to be no where near the idiot fest on the water, so it was just the waste of my time tracking it down.

TerryMSU