Trailer lights

[Bobbie Mayer]

When I picked up the trailer all but one turn light was working. Now nothing is.

I took off the light covers. Each light has a place for two bulbs. But there were only bulbs in one of each, and those were two-wire bulbs. I can't find a number on the bulbs. The bulbs appear intact. Do I stay with the two-wire bulbs or put one in each socket? (I tried moving the one bulb to the other socket and it still did not do anything.)

So: how do I go about troubleshooting? I know the lights are working coming from the car wiring as that connector has lights that blink to show you they are working. Then there is an adapter from the car plug (which is flat, with the 3/1 connector, to the trailer plug adapter (round to flat.) That was new in May.

Bobbie

[Bonnie]

Is there a fuse somewhere? That's what it sounds like to me.

Bonnie

[Bobbie Mayer]

If there is a fuse I would not know where to look.

I have not seen one. (And I know it isn't in the TV.)

Bobbie

[mikecontos]

You may need all bulbs installed to make a complete circuit. No bulbs may be causing an "open" thus interrupting the flow of electrical current. I would take the bulb that you have to an auto parts store and I just about gaurantee that they will be able to match it. If when all bulbs are installed the lights still dont work you may have a wiring issue. This is where my expertise is limited to tracing out each wire to make sure there are no breaks or disconnects. Look for in line fuses as well, my Hunter had one hidden beneath the forward bench where all of the wiring comes in.
Hope this helps...GOOD LUCK
Mike

[scott fraser]

I've had this problem with my rear signal and brake lights. They worked fine when I got the trailer but then quit. I found the bulb sockets were tarnished and a few were corroded lightly causing an intermittent connection. I used a .45 caliber brass brush in a drill to buff them up inside for a good connection. They seem fine now.

Be gentle when using the drill and brush though, you don't want to damage the socket. If you don't have any barrel brushes I think you could easily do it by hand with a bit of dowel wrapped in steel wool.

[Donna D.]

I found the bulb sockets were tarnished and a few were corroded lightly causing an intermittent connection.

I'd suggest using Dielectric grease in the sockets, available at any auto parts/hardware store... for less than $5.

[scott fraser]

I'd suggest using Dielectric grease in the sockets, available at any auto parts/hardware store... for less than $5.

Interesting stuff Donna, I'd never heard of it but will definitely apply some now that I've got the sockets cleaned up.
Thanks!

[Bobbie Mayer]

There is no sign of corrosion in the sockets. Also, the lights WERE working three months ago when I parked the trailer, except for one turn light. So I doubt it is either the lack of bulbs or corrosion, but I'll check.

I woke up this morning thinking, Hey, the trailer wasn't actually coupled to the car; maybe I didn't have a ground. Hitched it up and tried it, still no lights. So that wasn't it. It occurs to me it could be the adapter. I'm going to see if I can find a replacement for that and try it again. I think if I take the old one up to Napa and ask they can check it, though. I'm also going to get a test light. And of course look for a fuse.

This puts a hitch in my plans to get the wheel bearings repacked today- I don't dare drive to the repair place without either a registration OR lights, so I will have to wait to either fix the lights or get my 3 day pass (from Wed-Fri) for moving the trailer through Washington and Oregon. I'm going to try to call the Cal. DMV this morning, though.

Bobbie

[Bobbie Mayer]

Okay, so I went to Napa, got a nice helpful guy to look at the adapter. He told me it is supposed to (legally required to) be mounted on the TV. (The Napa guy who sold it to me didn't say so.) He also tested it and decided it works if grounded properly, but the right turn didn't work (which it didn't on the maiden trip.) So he suggested wiring a new four way connector in instead of the bad one.

I came home and did that. It still doesn't work. So now I don't know if it is the adapter or the trailer; and if the trailer, what the heck happened between now and May. So I called Les Schwab, who are going to repack the wheel bearings, and asked if they could look at it. They can, as long as it is something they can test or visible.

What I do if it still does not work, I have NO idea.

In the meantime, I'm off to the DOL to get a trip permit, since a 45 minute call to the Cal. DMV this morning yielded only the information that my registration is in the system, and probably will take three more weeks to finish processing. Oh, and the extra $19? $17 for a fee their automatic fee calculator left off, and a $2 penalty for not including the fee that their automatic online fee calculator left off.

Whose idea was this trailer, anyway???

Bobbie

[Brian B-P]

Whose idea was this trailer, anyway???

Certainly not the California DMV's... they seem determined to keep it off the road!

[Brian B-P]

...the lights WERE working three months ago when I parked the trailer, except for one turn light. So I doubt it is either the lack of bulbs or ...

I agree. The bulbs are wired in parallel, meaning their + contacts are all connected to the +12V source, and their other contacts are all connected to the return side of the circuit, so the current for any one of them doesn't pass through the others. That way, all bulbs work on 12V (if two were connected in series, they would need to be designed for 6V each... it isn't done that way in vehicles).

Often the wires are connected in a chain from one socket to the next, so a bad connection at one kills all the rest further down the chain. At each socket there's a fork in the wiring... one way into the that socket's bulb, the other way on to the next bulb. Break the wire connection coming into the fork, and there's no power for either way.

That's a more likely source of the problem. The return (often called "ground", normally white-insulated wire) side is the most likely culprit in this type of problem, because tail and left and right and marker lights can all be connected in the same chain. I lost most of my clearance lights for a while when I touched one of them...

[Roy in TO]

So now I don't know if it is the adapter or the trailer; and if the trailer, what the heck happened between now and May.

There are simple testers you can buy to show if your connector is working.
Alternatively you probably know someone with a trailer (boat & utility included) that you could test your Tow Vehicle connection with.

[Bobbie Mayer]

The four way connector is working- coming off the TV; it has a built-in tester.

Then it goes to the 7 way connector- that's what I don't know if is working. I bought a tester but I think it is the wrong kind and I don't know where to connect it anyway. Somebody help?

The guy at Les Schwab is going to look at it, but he suggested maybe a mouse ate a wire!

(I don't think so.)

I don't think I've knocked any wires loose but maybe I'll try all the connectors on white wires and see if anything helps. For one thing, there are wires (not white) coming out in the light boxes (I don't know what you call those, the place the bulbs go) that look like they ground to a screw but it could be either of the top screws and I don't know if it matters.

My back-up plan if I can't fix this is to postpone my departure, order wireless magnetic tow lights from U-haul, and not leave until they arrive (I want some for my boat trailer anyway so even after I fix the trailer I could still use them. I wish I'd done that a week ago, though.) The reason I didn't check the lights before is that they WERE working, and I didn't do the wheel bearings because I wanted them on the three-day trip pass.

Bobbie

[Paul from NWOnt]

When I first started reading this post, I would've bet you a nickel that it was a bad ground. I'm not ruling that out, but after reading that you're going from a flat 4 to a seven pin, I'd say that there's an issue with that as well.

The first thing I usually do when checking lights is "jiggle stuff". Hook up, start your vehicle, turn on your running lights and 4-ways. Remove the taillight cover, and jiggle the bulbs. Take them out, put them in, turn them, and wiggle them (BTW, I'd bet they're 1157's). Next, with everything still running, jiggle the connectors. Unplug/replug them a few times.

Lastly, if this hasn't worked, turn off your vehicle, and remove the cover from your 7-pin connector. Inside you should see that the wires are mounted inside little holes, and held in place with little set screws. Get yourself a small screwdriver, and loosen then tighten those little screws.

If all this 'jigglin' doesn't help, then I'd bet your 7-pin is wired wrong. Somewhere on here is a link to the industry standard wiring diagram for the 7-pin harness.

Or you could let the guy at Les Schwab look at it.

[Frederick L. Simson]

Each light has a place for two bulbs. But there were only bulbs in one of each, and those were two-wire bulbs. I can't find a number on the bulbs. The bulbs appear intact. Do I stay with the two-wire bulbs or put one in each socket? (I tried moving the one bulb to the other socket and it still did not do anything.)

If each light fixture has 2 bulb sockets, then the lower one (I am guessing that is where you found your bulbs, with the upper socket empty) uses 1157 bulbs with 2 filaments. One filament shines dimmer, and often has a brown wire feeding it; that is for the running or tail lights. The other filament shines brighter, and has a green (right side) or yellow (left side) wire feeding it; that is for the Brake and Turn Signals.

The upper socket would use an 1156 bulb with 1 filament. It is used for the Back-Up lights. If you have solid [b]RED lenses, then it makes sense that the upper sockets are empty. They're possibly not even connected.

These fixtures are usually grounded through the MOUNTING screws. There should be one white jumper wire to connect the ground to the base plate for each fixture.

[Byron Kinnaman]

When I first started reading this post, I would've bet you a nickel that it was a bad ground. I'm not ruling that out, but after reading that you're going from a flat 4 to a seven pin, I'd say that there's an issue with that as well.

The first thing I usually do when checking lights is "jiggle stuff". Hook up, start your vehicle, turn on your running lights and 4-ways. Remove the taillight cover, and jiggle the bulbs. Take them out, put them in, turn them, and wiggle them (BTW, I'd bet they're 1157's). Next, with everything still running, jiggle the connectors. Unplug/replug them a few times.

Lastly, if this hasn't worked, turn off your vehicle, and remove the cover from your 7-pin connector. Inside you should see that the wires are mounted inside little holes, and held in place with little set screws. Get yourself a small screwdriver, and loosen then tighten those little screws.

If all this 'jigglin' doesn't help, then I'd bet your 7-pin is wired wrong. Somewhere on here is a link to the industry standard wiring diagram for the 7-pin harness.

Or you could let the guy at Les Schwab look at it.

Boy does this drag up some old memories. Way back when I was a young buck working for my rich uncle. (Uncle Sam's military). I worked in a USAF Television station before the age of transistors. Something would go wrong with the transmitter and this sargent in charge would pull out his little stick. He would pound and yank on every wire connection he could find. After about an hour of this he'd get tired and go get a cup of coffee. While he was gone I'd replace the bad tube and spend the next hour resoldering all the connections he broke.
Thanks for memories.

[Frederick L. Simson]

There is no sign of corrosion in the sockets. Also, the lights WERE working three months ago when I parked the trailer, except for one turn light. So I doubt it is either the lack of bulbs or corrosion, but I'll check.

I woke up this morning thinking, Hey, the trailer wasn't actually coupled to the car; maybe I didn't have a ground.

Just because it did not look OBVIOUS, it does not mean that there was NO sign of corrosion. Just because the lights worked 3 months ago doesn't mean much now, either. Corrosion, like cholesterol, builds very slowly and evenly. There could be just enough of a microscopic film to prevent current flow.

Sometimes, especially through 4-pin to 7-pin adapters, the ground gets lost, and some older trailers grounded only through the frame, and they depended on the circuit being completed through the hitch ball-socket coupler connection. Good thinking to try hitching up and retesting.

[Byron Kinnaman]

Just because it did not look OBVIOUS, it does not mean that there was NO sign of corrosion. Just because the lights worked 3 months ago doesn't mean much now, either. Corrosion, like cholesterol, builds very slowly and evenly. There could be just enough of a microscopic film to prevent current flow.

Sometimes, especially through 4-pin to 7-pin adapters, the ground gets lost, and some older trailers grounded only through the frame, and they depended on the circuit being completed through the hitch ball-socket coupler connection. Good thinking to try hitching up and retesting.

And some don't even ground to the frame.

[Bobbie Mayer]

Well, I lucked out. I went home to try again (hooking up and testing) and caught the interest of a guy visiting next door. He works for the phone company but does things like this on the side, and he came over and helped, and we got as far as everything but one turn signal working. The rest WAS the ground problem; we think the ground wire to the four-way plug is maybe bad. I don't know why the left turn doesn't work but at least we're back to where it was a few months ago. (The left bulb is new.)

Bobbie

[Owen Lindsay]

You have the right idea in carrying a tester with you. When I bought my Trillium in the Early 80's we found the little cupboard above the closet. My wife dubbed it the GNW cupboard. {For God Knows What)
There is a small plastic bin in there where we keep the important things like spare mantles for the propane lantern, spare hose washers, the adapters for 15-30 amp power, a small can of 3in1 oil,
and a Ziploc sandwich bag which contains a paper with a diagram of the plug wiring, a 12v circuit tester, a roll of electrical tape, some small marrettes, a matchbox full of compression type wire connectors and a small pair of wire stripper pliers. There is still room in the bag for a couple of spare bulbs for each interior and exterior light on the trailer. This has been a lifesaver many times over the years. We also keep the registration and insurance cards taped inside the cupboard door for quick access if we need them.