Troubleshooting lights (my favorite: NOT.)

[Bobbie Mayer]

This is what I have:

both turn signals work, right is weak. (Weak signal or weak bulb?)
no tail lights
both hazard lights work
waiting to try brake lights in the dark but usually if hazards work, brakes work?

I have old splices I'm going to check and re-tape but I'm not sure what to do about the weak signal on the right.

Okay, I have read brown is tail lights so I'll make sure I get a good connection there. Just not sure what to do about the weak light. Try a new bulb? Assuming I can find one?

Bobbie

[Byron Kinnaman]

Originally Posted by Bobbie Mayer

This is what I have:

both turn signals work, right is weak. (Weak signal or weak bulb?)
no tail lights
both hazard lights work
waiting to try brake lights in the dark but usually if hazards work, brakes work?

I have old splices I'm going to check and re-tape but I'm not sure what to do about the weak signal on the right.

Bobbie

Hazard lights, turn signals, and brake light are all the same wires and light bulb filaments.
Running lights, trail lights are the same wire (circuit).
Turn on the lights of tow and check the side "running" lights and the tail lights. If they'll all not on then that should help lead to the problem.

The weak turn signal light could be as simple as a dirty bulb. However, I would suggest you start by replacing the weak bulb, the tail light filament could have burned out leaving a film on the inside of the bulb.

[Bobbie Mayer]

Tow lights work fine. Tail lights are not a problem I've had before (and at the moment not a major concern as it won't be dark when I'm driving.) But I just had the car wired and new hitch installed so it could be they goofed on tail lights. I guess I need a tester of some kind to see if that's the case? More likely its a wire.

I should replace the lights on the trailer one of these days as the covers are pretty much fogged (again, one is better than the other.)

[Ian G.]

Symptoms like this are usually a poor ground. Check your ground connections at the lights, at the connector to the vehicle and on the vehicle wiring at the plug.

Take a close look at the "dim" light to see if both filiments are glowing, if they are it is a sure sign it is a bad ground. The power feeds back through the second filiment and finds a ground through the light circuit at another bulb.

[Bobbie Mayer]

Only one filament lights up. Just not very bright.

I'll get a new bulb tomorrow and check the wiring where it is spliced. At least if I have turn signals and brake lights I'm safe as long as I'm not driving at night. But any ideas whether I can find replacement lights that fit the same screw pattern? These have four screws, about 5 inches apart, holding a square cover over the fixture, which is mounted on the back of the trailer (basically a metal plate with the bulbs.)

Oh, and there is only one bulb in each but two bulb sockets, but I think that may be because they used to have separate bulbs and now they have the two filament kind?

[Byron Kinnaman]

Originally Posted by Ian G.

Symptoms like this are usually a poor ground. Check your ground connections at the lights, at the connector to the vehicle and on the vehicle wiring at the plug.

Take a close look at the "dim" light to see if both filiments are glowing, if they are it is a sure sign it is a bad ground. The power feeds back through the second filiment and finds a ground through the light circuit at another bulb.

If it was a ground (meaning negative lead) no lights would work.

[Ian G.]

Originally Posted by Bobbie Mayer

Only one filament lights up. Just not very bright.

I'll get a new bulb tomorrow and check the wiring where it is spliced. At least if I have turn signals and brake lights I'm safe as long as I'm not driving at night. But any ideas whether I can find replacement lights that fit the same screw pattern? These have four screws, about 5 inches apart, holding a square cover over the fixture, which is mounted on the back of the trailer (basically a metal plate with the bulbs.)

Oh, and there is only one bulb in each but two bulb sockets, but I think that may be because they used to have separate bulbs and now they have the two filament kind?

you should not have to replace the light housing, just the bulb. The bulb should be an 1157 which has 2 filaments. They install with a simple push and twist using small studs on the sides of the metal base, the studs are offset where one is lower or closer to the bottom so the alignment of the bulb is correct in the socket. Maybe check to make sure the bulb is installed correctly, with force you can put the bulbs in 180 deg out.

Originally Posted by Byron Kinnaman

If it was a ground (meaning negative lead) no lights would work.

If the tail lights were a single filament bulb (an 1156 bulb) you are correct that the light would not work but on a double filament (1157 bulb) the power path will feed back through the second filament and backfeed the light on the opposite side. Because of the increased resistance of going through 2 filaments the light will very dim.

[Roy in TO]

Originally Posted by Ian G.

The bulb should be an 1157 which has 2 filaments. ...
the studs are offset where one is lower or closer to the bottom so the alignment of the bulb is correct in the socket.
... with force you can put the bulbs in 180 deg out.

If the tail lights were a single filament bulb (an 1156 bulb) you are correct that the light would not work but on a double filament (1157 bulb) the power path will feed back through the second filament and backfeed the light on the opposite side. Because of the increased resistance of going through 2 filaments the light will very dim.

That's a lot of force required, unless the socket is distorted. Easy way to tell is if you can see the "studs" in the slots on both sides of the socket.

Any chance the wiring or socket assembly is causing the 2 filament concept of dimness?

[Roy in TO]

Originally Posted by Bobbie Mayer

any ideas whether I can find replacement lights that fit the same screw pattern? These have four screws, about 5 inches apart, holding a square cover over the fixture, which is mounted on the back of the trailer (basically a metal plate with the bulbs.)

Oh, and there is only one bulb in each but two bulb sockets, but I think that may be because they used to have separate bulbs and now they have the two filament kind?

A picture would help for both.

I had a tail light once where the second socket was never wired up to anything. I think it was easier for the manufacturer to only make one design of the hardware and wire it differently for different models. I used the second socket to hold a spare where it could be easily found.

[Ian G.]

Originally Posted by Roy in TO

..... unless the socket is distorted....

My thought exactly, since the trailer is 42 years old the socket could be bent, worn or in general poor condition.

[Bobbie Mayer]

Here are the pictures. The one with no bulbs is the problem one. It's possible the ground wire wasn't screwed in but I haven't rechecked that yet. The one with one bulb works. It's cover is shown (less fogged than the bad one but also apparently with a melted spot in the cover? Covers are about 5 inches between screws, the one shown also includes the license plate holder.

[Bobbie Mayer]

I know the socket looks rusted but it worked far more smoothly than anything I had on the boat trailer ever did so I don't think that's the issue. And as I said, the second filament didn't glow at all so I don't think it was grounding through that.

[Bobbie Mayer]

Darn, got same photo twice. I don't know why but I'll go back to the ipad app and try again.

Okay, this is VERY weird. Ipad app shows the red cover instead of the duplicate photo showing up here. I'll try uploading it again.

[Bobbie Mayer]

See if this works.

[Bobbie Mayer]

Originally Posted by Bobbie Mayer

See if this works.

Something is VERY screwed up from Ipad app to here. I again posted the red cover and got a totally unrelated photo this time.

[Bobbie Mayer]

This morning, neither the new bulb nor the old worked at all. With or without the screw through the extra wire. I bought two new bulbs to see if both of those could be bad. Left turn is still fine and now I have a left tail light.

[RogerDat]

We just had a problem fixed, symptoms matched yours pretty much. One side weak, no running lights. We found problem source by confirming voltage at TV plug using a meter. Might be worth checking voltage at tow plug to make sure it's ok if you have not already done so.

Our problem was in TV, was told problem is common. Trailer uses two wires for something tow uses one (or other way round), so there is a module box that feeds the interface where tv has trailer plug wired in.

Module goes bad then no current to running light wire of plug on tv. Or very little, we showed < 2 volts, but it sometimes did work, briefly.

We had the problem with original cheap 4 pin plug that dealer put on and figured it was plug wire because I used tester and found almost no voltage on one pin and another was weak. We converted to 7 pin and problem was still there, guy that installed the 7 pin on tv just ran a wire to bypass the module box and feed the trailer plug or junction where trailer plugs are connected to tv wiring.

Good luck.

[Bobbie Mayer]

I don't think it is the TV as the problem with the right turn existed with the old TV and old plug, too. (Better not be as they installed it yesterday!) I haven't rechecked the splices yet, had to get good electrical tape, and will redo those this afternoon and try again. If it still won't work I'll check with the old tow.

[john warren]

those are a standard light, for the cost i would replace them and end my worries. as to any splices,,,,unsplice them clean to solid bare wire, the solder them and shrink wrap them.
abd sond or grind all grounds to bare metal, reatach them then liberaly coat them with dialectric grease to prevent them from rusting.

[Bobbie Mayer]

I haven't found the light fixtures yet though if I replace I'd just as soon do it with something brighter. But for tomorrow's trip that's not an option. I do have to get the right turn signal working again, though. I don't solder so that isn't an option, either, but I can wire them cleanly and hopefully that will solve the problem for now.