Scamp wiring issue

[llollio]

When I plug my Scamp into my Van the left turn signal won't work. I have tested the trailer using it's battery and it test great. I tested the van connection and it test great. When I connect the two, the left turn signal, when tested from the connector on the trailer side , shows no signal. If I remove the tail light the connection then shows a signal. It seems there is an issue between the grounds of the two vehicles. Both vehicles are wired correctly.
Anyone with any ideas?

Thanks
Steve

[Dan Meyer]

Hi Steve

What if you run a jumper wire between the frame of your van and the frame of your trailer? Do all of the lights work properly then?

Also, are both of the pigtail connectors in perfect condition? If not, I would replace them. In the typical installation they are subject to a lot of road spray and will corrode very badly in short order.

-- Dan Meyer

[llollio]

Thanks, Dan. I will try the suggestion you give and ground both trailer and van. The connectors have been replaced three times in the last week, hoping to resolve this issue.

[Brian B-P]

...If I remove the tail light the connection then shows a signal...

... which says to me that the bulb of the tail light is connecting two wires which should not be connected - perhaps what is supposed to be the ground of this taillight is actually connected to one of the other light circuits. I would, with the bulb removed and trailer unplugged from the van, use a multimeter on the resistance (ohms) setting to confirm that the ground side of the socket is really connected to the lighting ground wire, and that the hot terminals are really connected to the left brake/turn wire and the running light wire in the connector.

Can we assume that the same lights are used for brake and turn (no separate turn signals), and that the tail light bulb is used for both brake/turn and running lights (dual-filament bulb)? The Scamp wiring diagram in the Document Center shows the left light wire (red) and running light wire (green), but it also shows the auxilliary light wire (yellow), and I don't know if that is being used for separate brake light or backup light, or if it is even used on your Scamp, Steve.

[llollio]

Hi Brian, I think you may be getting me close to a solution. The trailer bulb is a dual-filament bulb and there is a second bulb, smaller, that I think is for back-up, though it's not connected from the van side. That would account for three wires.

Here's where I'm at present. I just isolated the basic two wires for the left/ right turn signals and the ground on both the trailer and the van. I then connected the two ground wires together and then using only the LEFT trailer signal wire, tested it first with the RIGHT van signal wire. It works great- the left trailer signal blinks. But, when I test it with the LEFT van signal wire it does not work.

I then put my light tester on the RIGHT van signal wire and got it to flash. I put it then on the LEFT van signal wire and it, too, worked. So, the van by itself seems to work fine.
Then I tested the trailer from the trailer battery, using the battery ground and jumping the hot line to the right and left trailer signal wires alternately. They both work fine. I got signal from both sides. This tells me that both the ground and hot wires going to each trailer light are functioning properly.

What's strange is that the van ground is the same for both the RIGHT and LEFT van signal wires but behaves differently when attached to the trailer. It works with only the RIGHT signal wiring.

Next I will run the test you suggest.
Thanks

Steve

[llollio]

OK> I just tried an OHM meter. I'm not sure if I'm doing this right, but I set the meter on it's lowest setting. When I touched the two prods of the meter they register .001. I then removed the bulb and disconnected the trailer from the van. I first tested the casing that holds the LEFT bulb- it registers .001. Then of the two terminals inside the bulb holder the left one also tested .001 and the right didn't register at all. Then I tested the RIGHT trailer side bulb holder and it tested the same.
What does this all mean?

Thanks

[Brian B-P]

You're doing great, Steve, especially for someone not who might not be familiar with test meter use. The lowest setting means the most sensitive (assuming you mean the range with the lowest number of ohms for a maximum reading), which is fine for this purpose. Touching the probes together is almost no resistance (a "short circuit"), so it reads nearly zero (.001 in this case).

I assume from your description that you are checking between the socket contacts and the frame - anything I say from here is based on that, and will make no sense if I have misunderstood. I was really thinking of going from the socket contacts to the wires at the front of the trailer to see how they are connected (takes a long test wire...), but I think we're learning valuable stuff here, anyway.

• casing (socket wall) to frame: no resistance - so the outer shell of the base of the bulb is connected to ground, which is what we want; also, the "ground" side of the light wiring is attached to the frame at some point, which may be what Scamp intended, but is not necessarily normal trailer practice
• the two terminals at the bottom of the socket each connect to a filament in the bulb...
  • one terminal to frame: no resistance - so the wire for one of the light functions (don't know if this is the brake/turn or the running light) is almost shorted to ground: this could mean a wiring short, but could also mean the tester current is going into the wiring, through the other bulbs used for the same function, and back through the ground wiring; that's exactly what should happen with multiple bulbs on the same circuit. With the several running light bulbs (the other tail light, plus all the marker lights) maybe this very low reading is okay if it is the running light circuit.
    
  • other terminal to frame: no reading (presumably what your meter shows for very high resistance) - so that terminal is not shorted to ground; with the only bulb removed, this would make sense for the brake/turn circuit

So where are we? The test is the same for left and right, and the right side works, so this seems to suggest that there is no trailer wiring problem. If the contact with almost no resistance to ground is the running lights (you may be able to see which wire goes to that contact), then everything looks as expected, which is consistent with the jumper test from the trailer battery.

By the way, I think that battery-driven jumper method of testing is a great idea if you are reasonably confident that you don't have any short circuit (big sparks if you do...), and the ability to do this easily is one reason I ran my wiring through a termination box which is easily accessible on the tongue.

What's next? Someone else may have an inspired suggestion, but I'm starting to wonder if we're working with some faulty assumption about which wire is which. I suppose it's possible that there is something really strange in the van wiring which only causes a problem with the trailer connected, but why only with the left side of the trailer wiring? I may have to start sketching circuit possibilies...

[Joe MacDonald]

when you test, this is what you should see:

with the bulbs out, and trailer disconnected starting on left(road) side
1) from the shell of the lamp holder to trailer ground, .001 ohms (or zero resistance.)
2) from one of the two pins(in the holder) to the same pin on the other light .001 ohms.
these are your running lights (markers) and are connected together before the plug. make sure they also show .001 ohms at the trailer plug
3) from the other pin (on left light) to the left turn wire on your plug, .001 ohms
this is your left turn signal wire.
4) from the other pin on the right (curb) side to the right turn wire on your plug, .001 ohms
this is your right turn wire.

do both your van and trailer share the same type of lights? same bulb is dual filament stop,turn marker, etc?
no orange or separate turn lights ?

You don't say what type of plugs you have, 4wire,6 wire or 7 wire.
there is a Scamp wiring diagram floating around somewhere

[llollio]

Boy, everyone, thanks for all the great ideas!
I have a 7 prong plug on the trailer going into a 7 prong on the van, which is actually a combo of a three prong (ground has been terminated) combined with the electric brake line, battery hot line and ground. The seventh wire seems to not be in use. I think it's for the back-up lites.
As to the bulbs, I doubt the trailer matches the van there's 22 years difference in age of the vehicles. Checking them is my next job.

Then I plan to check the voltage on both lights and look for a difference. Then on to the van, where I think the issue lives. I'll use a tail lite bulb and check the wires.
Thanks again for all your help. By this time next year I should be on the road.

Steve

[llollio]

Again, thank you to everyone for your generous help with my electrical issue. I have conquered the problem. Turns out it was a faulty device installed in the van that merges the brake wire with the two blinker wires. $26 later and a little dirtier, I am ready to hit the road.

The internet is awsome for obtqaining information for others of like mind.

Muchas Gracias, Danke and again, thanks.

Steve