Electrical Tinkering

[Win]

Here's the deal. I am at my Mother-in-law's house (Easter weekend) 400 miles from my M. So I brought a project with me for sanity sake. I keep a cheap (Harbor Freight) set of removeable trailer lights in my truck as back up for when (not if) I encounter trailer light issues. When plugged in each of the individual features of the light set work as they should.
1. Running lights turn on an off.
2. Right and left turn signals work as designed.
3. Brake lights function as designed.
However when the running lights are on, neither the turn signals nor the brake lights work.

So I finally took the lens covers off and discovered that when the running lights are on, the brake light and turn signals do in fact function. The problem is that the running light funtion of the bulb is much brighter than the brake/turn signal function. Therefore when the running lights are on, you can not see the brake/turn light going on and off.

Question.... What is the problem?
a. Needs different bulb?
b. Light set wired incorrectly?
c. Tow vehicle flasher not sufficient? I do not think I have this problem with boat trailer lights when
working. Plus I can't even find the flasher under the dash. Last time I replaced one was probably 1980.
d. Something else?

Disclaimer: I am an electrical dunce. If your answer envolves using a test light or meter (both of which I have) please include step by step instructions. (I love tools, even if I do not know how to use them).
As always this board and its members are a veritible fountain of knowledge and help and I appreciate all the help available here.

Win

[Hardcrab]

Either the bulb is in the holder wrong, or it's wired backwards.

The bright filament is the brake/turn filament, the dimmer filament is the running light.

The bulbs are designed to only go in the holder one way.
The "bayonets" on the brass are at different heights as are the slots in the holder.
The bulbs can be forced backwards if you really work at it I suppose.

If that's not the problem, then swap the running lights wire and brake/turn lights wire at one end or the other.

[GART]

You have an EARTH (--) problem.
the power is getting to individual lights, but too much resistance on the return when more than one light on.

[mastreb]

This is quite simple: The running lights operating resistance is much lower than the other lights.

Electricity is like water in that it will flow through the lowest resistance first. When the running lights are on, electricity prefers to flow through them because the lightbulb is a lower resistance type.

You need to balance the resistance with a different type of lightbulb. The way to test is to take an ohmmeter (or multimeter) and determine the resistance of each of the different functions. That will tell you what "ohm" rating the running lightbulbs need to be.

When the resistance matches, electricity will flow through all paths equally.

Matt

[Retcoastie]

Win,

The answer is probably (a). This can be corrected by changing the bulbs or changing the wires. So (b) would also be a right answer. It is just that (a) is an easier fix.
That makes Hardcrab's explanation correct. The two bulbs are the 1016 and the 1157. The 1157 is by far the most popular as it is brighter. If you have 1157 bulbs, I would change the wiring. If you have 1016s, change the bulbs.
Gart is probably incorrect. If both filaments light up but the running light is the brightest, there is an adequate return current path. The filaments are getting the wrong power to them.
Matt is right in his explanation but wrong in his statement.

The running lights operating resistance is much lower than the other lights.

In fact, the running lights are supposed to have higher resistance. I'm not sure if he is talking about what you actually have (the problem) or what is correct (the fix). The higher resistance light is the dimmer light. What you want is the running light power to be going to the higher resistance filament and the stop/turn to the lower resistance filament. When holding an 1157 bulb in your hand with the lower index pin or peg facing you, the contact on the left is the filament contact for the stop/turn and the one on the right is the tail/running filament.

Hope this helps.

Ken

[K9Kampers]

GART is right, at least in where to start. First two things to check with electrical problems - supply voltage & adequate ground. Most trailer light issues are the result of faulty ground connections. First & easiest thing to check / confirm / fix. Replacing wires & bulbs isn't going to solve anything if the ground is faulty.

[Hardcrab]

This is not rocket science, just a light bulb for goodness sakes.

The bulb in question is a two filament bulb being fed from two different circuits.
One dimmer (running) and one brighter (brakes/turn signal).

I take his symptoms, as he described, to mean the running lights power is going to the brighter brake/turn filament and the brake/turn power is going to the dimmer running filament.

His description fits well to either end being wired backwards, (just as his lights are acting).
Duh.

It's somewhat of a strech to have any esoteric answer beyond that, IMHO.

Now, if he had said he had no lights, then lets all jump on a ground (common to both) issue.

[Catigale]

Bad grounds are by far the most common problem in trailer wiring. The presence of some light function is NOT a good diagnostic for a good ground. I have vanquished most of my trailer light demons by wiring ever single one of my trailers with a hard separate ground wire to each light and making a single common point of connection up on the trailer tongue where the harness connects.

[Win]

Hi Everyone,
Thanks for the input so far. I think I can put the ground issue to bed. This light set is portable (magnetic) and designed to be easily removed. The ground wire is a direct connect from the tow vehicle and runs to both lights. I know that it works because if I disconnect the ground (white wire) from the light none of the functions work on the light with the disconnected ground. All individual functions work with the ground wire connected.

I also know/think the tow vehicle end is wired correctly because the lights on my 4x8 utility trailer work as expected with or without the running lights on.

So, is it the bulb or is the light set wired incorrectly? It is very possible that the lights are incorrectly wired. Remember this is a Harbor Freight product made in China. When on sale it's only $9.95.

I think I will buy a 1157 bulb on the way home from work tonight because it's the easiest to test. If it is the wiring, how do I fix it? I am at work now and I have not tried to see how the running lights (Brown) wire and the brake/turn light (Green or Yellow) wire is connected to the fixture that hold the bulb. Probably soldered? Do I just reverse this connection?

Again, thanks for all your help.

Win

[Hardcrab]

Here's a stab at your fix.
I will assume you KNOW your tow vehicle has worked fine in the past.

It is a wild 0% chance that your two exisiting bulbs are made wrong from the gitgo, but if you want to buy a new one to check then your call. They just might be installed backwards in the "one way only" holders (with much mechanical effort).
Not likely at all, but at least look perhaps.
We do know that they work fine, as far as lightbulbs go, just working backwards.

The mfg prolly got the wires at the holder on the wrong terminals in each housing; much less likely a mistake at the plug end.
Perhaps it was assembled by a new slave labor worker that day.

By that I mean the brown wire (both sides running lights) is on the yellow (left brake/turn) / green (right brake/turn) terminal and therefore the yellow/green is on the brown terminal .
The white ground wire is as fine as it gets. No problems there. Look elsewhere.

If they are soldered, and you know how to solder, simply swap the Brown/Yellow on the left side and Brown/Green on the right side.

If they are induction welded or some such thing, then I would cut the wire a few inches fron the holder, (but still inside the housing) and re-splice as above.

All in all, a pretty simple repair IMHO.

[Highlander]

Most of the tail lights have two wires the r/s will have a green wire for the brk/ signal & black wire for the tail light if you also have a white wire its your ground wire if no ground wire then the light base must be grounded by its self or through the frame the l/s light will have a yellow wire for brk / signal & black for tail light. your either wired up back wards , bad ground , loose conection some where a bad bulb "brkn filliment shorting accross the other" or your vehicle has a problem . Test the lights with a battery direct to see if the problem still exists this should eliminate the vehicle

J
PS I just made up a light bar with LED'S that hanges across the back of the boat great for when in bumper to bumper traffic
http://s844.photobucket.com/albums/ab1/ ... 010019.mp4

http://s844.photobucket.com/albums/ab1/ ... 010018.mp4

http://i844.photobucket.com/albums/ab1/ ... 010016.jpg