Trailer lights

[john]

I have a problem with my trailer lights.The lights work but not properly. The turn signal works as its suppose to.The running light is too bright and is really running as my brake light.I hit the brakes and nothing happen light wise.The trailer is 5 years old.No one has messed with the wiring.The problem is on one side. I have changed bulbs to make sure thats not the problem.I have cleaned the contacts etc. Pulled another guys boat 2 weeks ago so my wiring on my truck is not the problem.Any thoughts? I might add that I hate, I mean HATE messing with trailer lights. Thanks

[asc]

Check to see if the bulb is in backwards because I had the same problem and turned the bulb around and it worked fine. And luck is also needed with lights.

[rickn]

Sounds like something isn't grounded..... any time goofy things start to happen, look at grounds.

[perchjerker]

Yep, grounds are usually the culprit. One thing a lot of people overlook is a ground problem or short within the bulb itself. If you are sure the grounds are good, try replacing the bulbs (all of them). Do you have a 12 v test light or voltlmeter to make sure power is going where its supposed to be? Current looks for the path of least resistance, remember that in your diagnosis.Sounds like that path is the running light in your case. Sometimes if you have a bad ground, the path of least resistance becomes one of the other filaments in the bulb, can cause crazy things!

[Ray]

You definately have a ground problem. Very common on boat trailers. You have two things you can do: replace the insert on the lens, or pull the insert out and clean up with a wire brush. And clean all connections going to the lens. Clean the plug, too. You said its five years old, if they last that long I would just go out and buy the whole new lens. Once currosion starts to set in, you'll have nothing but problems. Ray

[john]

The lights on my trailer are supose to be sealed. They didn't seal so I opened the housing so I could change the bulbs. I did this 4 years and haven't had a problem to now...The bulb can't be put in wrong, it won't sit in the socket. Now, I have three wires coming from the back of the light. All of them immediately go into the trailer. So where am I looking for the groud problem? In the light it self or the whole trailer ground? Remember the other side work correctly. Thanks

[perchjerker]

Could be a bad bulb, a filament could be shorted or open and the current is finding its way to ground through another filament. Usually the light assy is grounded with the bolts that attach the bracket to the trailer. Try unbolting the socket and sanding the surface that contacts the trailer and reconnecting everything. Also you might try grounding the metal socket to a clean ground spot on the trailer with a jumper wire and see if it changes anything. I am assuming you are using 1157 type bulbs with a metal base, not the plastic kind found on late model autos, correct?

Incase you didnt know:

Brown- running light & licence plate light
Green- right turn & stop
Yellow- left turn & stop
White- ground

4 pin flat plug color code for most trailers

[john]

The whole sealed unit is made of plastic. Its designed to quickly snap out so you can change the whole thing.The light inside is the one you mentioned perchjerker.The only problem with the ground is if the groud wire is loose behind the plastic mount, other than that im stumped. Probably time to replace the unit. I did try another bulb I had. It did the samething. Another thing I found out is it takes about 10 seconds for the bulb to so hot you can't touch it!!

[Fenwick]

I think you have a short also. However I think one or more wires that run through the frame have worn thin. As far as I know this means you will have to replace the whole side. I would do both sides on a five year old trailer. A lot of places cary a complete wire set for trailers. Good Luck, Fenwick.
Fenwick

[rickn]

If I remember correctly. the bulb is grounded thru a rivet in the light housing. I have used a hammer and punch to tighten these, but if thats where it is loose, you need a new assy.

[Starfish]

Before you tear into your trailer too far, I'd suggest plugging your trailer into someone else's truck first to make sure it's not your rig's fault. Sometimes a diode will burn out in the converter box feeding your trailer plug, and it really messes things up-- sometimes on just one side, sometimes both. If you don't have access to another vehicle, take a voltage meter and check each of trailer plug connectors (on the truck) against the ground connector while turning on the lights, hitting the brakes, turn signals, etc.-- make sure all the signal outputs are doing what you expect them to.

Good luck-- nothing's worse than an "unexplained electrical phenomenon"...

[perchjerker]

Good post, starfish. While you have the meter, set it on ohms and check for proper continuity in the harness also.