Scamp wiring conundrum

[nigeleccleston]

1997 Scamp 13 street-side rear light assembly. The flasher does not work for the turn or hazard lights.
However - when I check the voltage between the brown wire and ground wire, I get a (flashing) 11+ volts. But then, if I touch the black wire from the light assembly to the brown wire, without changing anything else, the voltage disappears completely. Remove the black wire and my meter flashes 11 plus volts again.

My first thought was a bad light assembly. But I mounted a taillight assembly that definitely works (from curb side) and got the same result. Also used a bulb that definitely works.

The running light on that same assembly works. The trailer was hitched to my TV and I had the ignition on. In case it makes a difference - my Scamp does not have a power converter.

I don't know what to check next!

(This is related to my previous post about 1156 bulbs but I think this is a different topic)

[John in Michigan]

Nigel,

I believe the Scamp (and Boler and Trillium) wiring colors correspond as follows:

Yellow: center auxiliary
Green: tail and license lights
Brown: right turn and stop lights
Blue: electric brake
Black: battery charge
Red: left turn and stop lights
White: ground wire

With that in mind, its no surprise that there would be no voltage between the brown wire and the black wire...

-John

EDIT: White wires in the camper are for 12vdc negative/ground/return, while black wires in the camper are for 12vdc positive.

[floyd]

DOT wiring is separate from house wiring... think "fourplug" when wiring DOT lights.

[Joe MacDonald]

Start simple, get an LED tester that plugs into your tow vehicle trailer plug and make sure all is functioning there first (this should cost $10.00 or less)
then find the first junction point where your wiring enters the trailer and confirm that all connections are good(remaking if necessary) and check at that point with a meter. with most 12v wiring the problem is usually a bad ground wire. this can cause symptoms like you are describing. Run a temporary ground wire from your TV to the trailer rear end (lay it on the ground) and use this as your ground reference, then check the signal and marker light wires.
I find it better to check the wires by themselves, without a fixture attached.

Joe

[nigeleccleston]

The light assembly itself has a black wire leading to the 1157 bulb. On the street side the brown wire is attached to it; on the curb side it is a red wire. I have a 4-pin, so no electric brake

Originally Posted by John in Michigan

Nigel,

I believe the Scamp (and Boler and Trillium) wiring colors correspond as follows:

Yellow: center auxiliary
Green: tail and license lights
Brown: right turn and stop lights
Blue: electric brake
Black: battery charge
Red: left turn and stop lights
White: ground wire

With that in mind, its no surprise that there would be no voltage between the brown wire and the black wire...

-John

EDIT: White wires in the camper are for 12vdc negative/ground/return, while black wires in the camper are for 12vdc positive.

[nigeleccleston]

Thanks Joe, I'll try the temporary ground wire. I did check the wires with a multi-tester with no fixture attached - same result. With no fixture, there was voltage when I measured across the brown wire (that carries the right turn/brake signal) and the white ground wire.
The TV plug is good - I've been using a set of magnetic turn/brake lights while I figure out how to fix the trailer light.
Also, everything works fine on the left turn/brake light.

Originally Posted by Joe MacDonald

Start simple, get an LED tester that plugs into your tow vehicle trailer plug and make sure all is functioning there first (this should cost $10.00 or less)
then find the first junction point where your wiring enters the trailer and confirm that all connections are good(remaking if necessary) and check at that point with a meter. with most 12v wiring the problem is usually a bad ground wire. this can cause symptoms like you are describing. Run a temporary ground wire from your TV to the trailer rear end (lay it on the ground) and use this as your ground reference, then check the signal and marker light wires.
I find it better to check the wires by themselves, without a fixture attached.

Joe

[redbarron55]

You may have a bad ground wire, check with an ohm meter.
Also check the turn signal wires with that same ohm meter.
Over the years haywired splices may have failed and especially ground connections corroded.

[ThomasBalmer]

On tow vehicles with separate stop and turn signal lights, there may be an aftermarket device to combine the functions into one trailer light for your 4-wire trailer hook-up. These do not have high amp ratings. If your trailer has double sets of tail lights, the turn signals can exceed the amp limits. If that is the case, you have to switch the trailer stop/turn signal bulbs to LED, to lower the amp draw.


These devices have an automatic breaker that takes i few moments to trip, and resets when cool, so it can fool you into thinking everything is OK, then it stops.

[Mike_L]

The most common cause of electrical problems in trailers is a faulty ground. Second is someone who shouldn't make changes to the electrical system doing so.
Confirm the wiring harness on your tug is working properly and work your way back. I agree with the advice previously given, run an independent ground from your tug and check each lead at the light.

[nigeleccleston]

I ran a wire over from the red turn/flash wire on the curb side and the street side flasher works. So the problem is with the brown wire. I still don't understand why I get 12 volts from that brown wire when the light assembly isn't hooked up but I'm content to let it remain a mystery. Thanks for all your responses!

[Lockman]

Nigel,
If I read your post correctly you stated that you read a pulsing voltage between the brown wire and gnd. (white wire). You then for some reason attached the black wire to the brown wire and then read from those two wires to gnd., no voltage. You actually bridged two separate circuits into one, can't do that. You should measure between the black wire and gnd. to get a voltage reading when the running lamps are on.



The 1157 lamp has two independent filament circuits and if you look at the base of the bulb you will see the two separate connections. You have to make sure that you are using the correct bayonet base socket for the 1157 lamp. The outer shell of the base is gnd. and there are two separate wires that go into the base of the socket to mate with the lamps two contacts. That why the 1157 will only go into the base socket one way, the locking pins on the lamp are off set from one another to properly seat the lamp and connect the wires to the correct filaments in the lamp.


If you do not have two wires coming out of the base of the socket it must mean that its not the correct socket for your application. One for the running lights and the second for the brake/turn signal/hazard light.

[John in Michigan]

Originally Posted by nigeleccleston

I ran a wire over from the red turn/flash wire on the curb side and the street side flasher works. So the problem is with the brown wire. I still don't understand why I get 12 volts from that brown wire when the light assembly isn't hooked up but I'm content to let it remain a mystery. Thanks for all your responses!

The brown wire should only have power when the camper is plugged into the tow vehicle and the turn signal or brake or hazard/flasher is engaged. Are you saying that the brown wire has power when NOT plugged into the tow vehicle? That would be a problem, e.g., the brown wire might be shorted to the battery. The 4-pin connector on the camper side should be wired:

Green: tail, license and side marker lights (positive +)
Brown: right turn and stop lights (positive +)
Red: left turn and stop lights (positive +)
White: ground wire (negative -)

[nigeleccleston]

Originally Posted by John in Michigan

The brown wire should only have power when the camper is plugged into the tow vehicle and the turn signal or brake or hazard/flasher is engaged. Are you saying that the brown wire has power when NOT plugged into the tow vehicle? That would be a problem, e.g., the brown wire might be shorted to the battery. The 4-pin connector on the camper side should be wired:

Green: tail, license and side marker lights (positive +)
Brown: right turn and stop lights (positive +)
Red: left turn and stop lights (positive +)
White: ground wire (negative -)

Thanks John, no, I had the Scamp on hitch and plugged in to the 4-pin the whole time. And would turn on whatever I was testing, including wedging a pole between brake pedal and seat to even test that. The brown wire has voltage, though I didn't measure amperage yet.

[nigeleccleston]

Originally Posted by Lockman

Nigel,
If I read your post correctly you stated that you read a pulsing voltage between the brown wire and gnd. (white wire). You then for some reason attached the black wire to the brown wire and then read from those two wires to gnd., no voltage. You actually bridged two separate circuits into one, can't do that. You should measure between the black wire and gnd. to get a voltage reading when the running lamps are on.



The 1157 lamp has two independent filament circuits and if you look at the base of the bulb you will see the two separate connections. You have to make sure that you are using the correct bayonet base socket for the 1157 lamp. The outer shell of the base is gnd. and there are two separate wires that go into the base of the socket to mate with the lamps two contacts. That why the 1157 will only go into the base socket one way, the locking pins on the lamp are off set from one another to properly seat the lamp and connect the wires to the correct filaments in the lamp.


If you do not have two wires coming out of the base of the socket it must mean that its not the correct socket for your application. One for the running lights and the second for the brake/turn signal/hazard light.

Thanks - the black wire I referred to is just one of the filament circuits to the 1157. So it is what the brown wire should be attached to. And that black wire is attached to the correct filament - it worked when it was on the curb side of the trailer.
To explain why I moved it - the license plate tabs were broken off and I purchased a new rear assembly. I was having problems with the street side lights so I swapped that assembly with the old, working curbside assembly, hoping that would be all I needed to do. .

[Lockman]

Nigel,


Could you post some pictures of the wiring into the tail light assembly, inside the tail light assembly and also of the wiring coming out of the camper that is going to the assembly? It certainly would help explain things.

[nigeleccleston]

Hopefully pictures will appear..
First pic - Bargman 98 series tail lamp, Scamp original issue. The upper bulb is for reverse and is superfluous since I only have a 4-pin connection. Lower bulb is the tail/turn/brake. A ground runs from the back of each strip directly into the trailer.
Three pics of the inside wiring from different angles. Green supply connects with green wire to running light of 1157 bulb which does work. White main ground connects to the two grounds from rear of assembly. Yellow supply (reverse light) connects with red wire going to 1156 bulb. Brown supply connects to black wire going to 1157.

Since my last post I tested continuity of the brown wire all the way to the 4-pin connector (where it connects to the green supply from the TV). 0.018 ohms, so it should work.

[John in Michigan]

Nigel, I think you previously said that the bulb was OK. Its possible you have a break in the black wire or its associated connector that penetrates the 1157 bulb base. Or possibly a short between the black wire connector that penetrates the 1157 bulb base and the ground portion of the bulb base.

[Lockman]

Nigel,
Is it possible that the black wire going to lamp housing is pinched? If the running light works it has to mean that the gnd. circuit is ok, unless the gnd for the 1157 lamp is open and not making good contact where its connected.
But that would not be the reason you lost your pulsing voltage. But a short in the black wire certainly would.



Besides that everything looks OK wiring wise.

[Lockman]

Nigel,


I would suggest:


With everything connected for normal wiring, no voltage applied.


1) Disconnect the 4 pin plug at the trailer

2) With your ohm meter, connect neg lead to gnd on the 4 pin plug, use an alligator clip if necessary.
3) Measure the resistance through the lamp circuit to ground on both directional circuits. you will have to know which wire goes to which lamp.

4) Compare results they should be the same. If not then there is a problem.
5) If there is a problem, a lower resistance, - possible short, high resistance, - possible open.



Let us know what you find.

[nigeleccleston]

Originally Posted by Lockman

Nigel,


I would suggest:


With everything connected for normal wiring, no voltage applied.


1) Disconnect the 4 pin plug at the trailer

2) With your ohm meter, connect neg lead to gnd on the 4 pin plug, use an alligator clip if necessary.
3) Measure the resistance through the lamp circuit to ground on both directional circuits. you will have to know which wire goes to which lamp.

4) Compare results they should be the same. If not then there is a problem.
5) If there is a problem, a lower resistance, - possible short, high resistance, - possible open.



Let us know what you find.

Aha! At the 2K setting gReen (right) read 0.040 and yeLlow (left) read 0.002
At the 200 setting right was 34.4 and left was 0.9
So... replace the brown wire? A hassle running it behind all that rat fur. Tomorrow I'll splice a wire right at the 4-pin and run it direct to the lamp. If I see a turn and brake signal I'll know the hassle will be worth it!
A side note - I hooked a 12V battery to the offending light's black wire and it shone bright so I am confident the problem is not in the fixture itself. Thanks!