trailer wiring

[waltpm]

Electrically challenged sailor needs help. Just took the boat out of storage and found that the brake and directional lights on the trailer don't come on. The running lights do come on . Using a battery connected directly to the light I verified that the bulb is OK. What would be the likely cause of this problem?

[DLT]

tow vehicle fuses?

[James V]

Bad ground. See if you have power to the bulb. Try running a seperate ground wire to where the ground is on the trailer.

[Bobby T.-26X #4767]

my lights didn't do nothin' last week when i hitched up.
the first place i went to was the ground location from the truck connector to the trailer.
that was it, and usually is.

on another note, i noticed that the nuts on lugs of my lights are completely frozen. the lights work fine but there's no way that i'll ever be able to remove them from the trailer without breaking the light.

any thoughts?

Bob T.
"DaBob"
'02X w/ '04 90-TLDI

[waltpm]

If the ground or fuses were bad I wouldn't have running lights would I?

[mike uk]

I assume you have a plug and socket to connect the wiring between the trailer and the tow vehicle. Faults in this plug and socket can occur very easily arising from corrosion of the terminals and/or cable. Check the socket on the tow vehicle first because that seems to suffer more than the plug on the trailer side. If there's rust on the terminals, renew the socket and cut back the cable to good clean copper. The new socket should have the universal wiring colour codes on the packaging (at least they do in UK).

Mike

[Catigale]

Hello Walt - check all the contacts (truck, connector) for corrosion and get them all nice and shiny..it helps to have a helper watching the lights while you wiggle theto see if they flash a bit - that can help you isolate the problem to the correct place at least.

Ive learned to give up on using ground points on trailers and run separate ground wires back to the connector - it cost some wire but eliminates a lot of hassles.

email me too - I am in Buffalo once a week on business and usually free evenings (stay around Sweet Home area usually) so can give a hand to a fellow mac'r of course..

[DLT]

If the ground or fuses were bad I wouldn't have running lights would I?

Depends...

You might have a ground connection to some of the lights but not others... These trailers are grounded through the frame. So, I'd suspect that the most common ground failure is 'no ground anywhere'. But, it is possible that one fixture has a sufficient ground, while the other does not. What is highly unlikely (if not impossible) is for once function of a light to work, such as running lights, when another function of that same fixture does not, such as brake/turn lights.

You said that you tested the bulb, which would be another good source of failure. Each bulb likely has two filiments, one for running lights and another for brake/turn lights. If you got both to light, then that's not your problem...

So, the only other thing I can think of is tow vehicle fuses. My truck has separate fuses for the trailer connections and the truck's own lights. So, my truck's turn signal can work fine, while my trailer's does not...

By the way, how did you test the lights? You said you used a battery, but where did you connect it? If you tested through the trailer's wiring, then you just ruled out a bad ground... If, on the other hand, you pulled the bulb and wired it directly to the battery, then you might want to try it the other way after you've checked all the fuses...

[Bobby T.-26X #4767]

[You might have a ground connection to some of the lights but not others... These trailers are grounded through the frame.

i've had that happen to me on several occasions.
one side works, the other doesn't.

in the past i completely removed the light from the trailer, cleaned the trailer surface to bare metal, and got it to work fine.
now, the nuts are frozen onto the bolts. everything spins, can't remove them.

so the next time it happens to me, i'm pretty much screwed and will have to buy new lights.

Bob T.
"DaBob"
'02X w/ '04 90-TLDI

[James V]

i noticed that the nuts on lugs of my lights are completely frozen. the lights work fine but there's no way that i'll ever be able to remove them from the trailer without breaking the light.

Go to one of the better auto parts stores and ask what is the best rust remover/anti-seize, get that and a small wire brush. Apply and reapply until rust is gone and it loosens up. Protect ALL surfaces from the rust remover as it can damage paint, wires, plastic ect....

You also might want to price out new trailer lights. It looks like you may need them in the near future.

[Chip Hindes]

now, the nuts are frozen onto the bolts. everything spins, can't remove them.

so the next time it happens to me, i'm pretty much screwed and will have to buy new lights.

One of my tail running lights is out; I got a new sealed capsule (actually got two, for when the other one goes as well, $7.99/ea from Champion compared to $14.99 ea for the whole light) but I discovered the same as you, the nuts on the carriage bolts holding the light housings are frozen solid, and they just spin in the housing when trying to remove.

I've got two things I'm going to try.

First, I believe the capsule is replacable without removing the light housing from the trailer; the only reason to remove the housing is to access the ground, which is held captive under the light housing. I'm going to try ignoring the existing ground swire, and simply run a separate ground to the new capsule.

If this doesn't work, I'll cut off the nuts with a die grinder and replace the carriage bolts with new ones. Maybe stainless, maybe not; the originals have lasted six years with only one burnt out bulb; might be hard to justify the cost of stainless.

I'll let you know the success/failure.

[craiglaforce]

Walmart sells a small LED diagnostic trailer light plug connector. Just plug it into the tow vehicle connector and it easily tells you if the truck wiring is working. These are often fed by different fuses. I think the connector is pretty cheap.

Also concur that running a separate ground wire from the truck frame to the trailer ground pin is a good idea.

Other than that it is just a matter of checking all the trailer connections and maybe replacing the lights.

[baldbaby2000]

Check the ground just to be sure. Sometimes the running lights will still come on (albeit dimly) because the bulbs have a common ground for both the running light filament and the turn signal filament and the turn signal filament may provide a return for the current through the vehicle's lighting system.

[Billy]

Basically the same just happened on my trailer. Turn/brake worked but no running (tow) lights. On F series Ford trucks there are several separate fuses in 2 different boxes. Turned out the blown fuse was located in the box under the hood next to the brake resevior. Not under the dash where I spent 20 minutes checking every fuse. Maybe this will help. Good Luck.