OT - Voltage Drop In Trailer Wiring

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On 8/17/2013 6:47 PM, Nate Nagel wrote:

...snip...

...Snip ...

There's a link to a pic included below.
Follow this 4-step logical progression and tell me if you think it makes sense. Obviously a call to Bargman should clarify everything. I plan to call them on Monday.
1 - The part number on my fixture is 30-84-022, which tells me it's an 84 series fixture.
http://i440.photobucket.com/albums/qq121/DerbyDad03/BargmanTaillight_zps9942fb32.jpg
2 - I found an RV forum where a poster said he replaced his 30-84-022 with a 47-86-101 LED fixture and that it was an exact fit. I've looked at the Bargman site and it looks like the 47-86-101 should work, but mine is an 84 series, so I'm not sure.
http://www.bargman.com/content/products.aspx?lvl=3&parentid=0&catID 20&partH-86-101
3 - The replacement part listing for the 47-86-101 shows just the LED lens with a part number of 47-84-420. Note the "84". This is just the LED lens with bare wires.
http://www.bargman.com/content/products.aspx?lvl=3&parentid=0&catID 20&partG-84-420
4 - Bargman also makes a "upgrade" LED lens with an 1157 plug that fits the existing socket in my 30-84-022. The part number is 42-84-410.
http://www.bargman.com/content/products.aspx?lvl=3&parentid=0&catID 20&partB-84-410
My conclusion:
If the replacement LED lens (47-84-420) for the full replacement LED fixture (47-86-101) is nothing more than the upgrade LED lens (42-84-410) without the 1157 plug, it would be a waste of time for me to replace the entire fixture and have to wire it in. As long as the socket is in good shape, why shouldn't I just buy the upgrade LED lens? Two screws, a "bulb twist" and I'm done.
Am I'm missing anything in that thought process?
Thanks.
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On 8/16/2013 7:39 PM, DerbyDad03 wrote:

So unless you have a new trailer, why not just replace the whole socket assembly. Sockets deteriorate over time. Some of the new lights are much nicer than putting a plug in bulb in. They over more leds so if one fails you still have others.
--
Jeff

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DerbyDad03 wrote:

Hi, Remeber Ohm's law? Use it.
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On Fri, 16 Aug 2013 18:34:15 +0000 (UTC), DerbyDad03

The 2 volt drop at the plug indicates undesized wiring in the tow vehicle or poor connections. I'd bet on a combination of the two. The scotchlock connectors used by most installers are CRAP and make a high resistance connection - and most cars are wired barely heavy enough to handle the OEM lighting load.
As for the extra drop to the lamps on the tailer, most likely ground issues - 2.5 ohms on a 12 volt 36 watt tail lamp circuit (3 amps)will cause a voltage drop of 7.5 volts, so if you DO have a 2.5 ohm resistance in the ground the trailer has to be getting part of it's ground through the ball hitch.. I'd take a set of good booster cables from a good clean spot on the trailer frame to a good clean spot on the tow vehicle frame and see what it does for your voltage at the bulb.
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On 8/16/2013 2:34 PM, DerbyDad03 wrote:

2.5 ohms is a lot when you're talking about 12V systems; V=IR so if you are pulling an amp or more (extremely possible, unless you are using LED lighting on your trailer) that's a 2.5 volt drop right there. Time to break out the deoxit, abrasive of choice, and some grease...
if the trailer is steel you might want to just go ahead and run a ground wire connecting all the ground points together.
nate
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wrote:

I think he said it is aluminum - and tying all the clearance lights together would be a major job..
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My entire post was part of your response and is part of this one.
I'm not sure what made you think I said it was aluminum.
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I would buy ONE and just try it......
Although if the trailer is older I would just rewire it, add dedicated grou nd wires to not only the trailer but the tow vehicle, with proper soldered wires and heat shrink tubing.....
like i said if the traier is older sometimes its best to start over...
the side marker lights arent as likely to have wiring troubles since most o f the wiring is up high away from rain water and deicing chemicals.... but still replace them with Leds. Look at this as a one day interesting project . while your at it fix anything else thats broke or failing like hinges and locks, and check the underside and roof for rust, and check the ires if th ey are old replace them and repack the wheel bearings.... while checking th e trailer jack and restraint chain/////
a few years ago a tree chipper trailer came loose and killed 3 or 4 people. ..
maintence is key to safe operations I found one trailer with flakey lights where much of the wiring was rotting away. undoubtedly from salt water exposure
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Other people have mentioned the tow vehicle ground. I have a question...
My tow vehicle has a factory installed connector in the wire harness for the trailer wiring. This cable and converter plugs right into that connector.
http://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Tow-Ready/118336.html
With that setup do I need to be concerned about the vehicle ground or anything else related to the vehicle wiring? Is it (normally) safe to assume that the factory installed harness is properly wired?

I'm way ahead of you, Bob!
The lights were the last task in my periodic maintenance exercise. The tires are fine and inflated to proper pressure - including the spare, the wheel bearings were repacked, the hinges and other hardware were removed, wire wheeled and coated with RustOleum Cold Galvanizing Compound and the fenders were removed painted. While the trailer was on the jack stands I inspected the underside, the axle, etc. I checked the safety chains and their connection at the trailer. It all looks good.
Funny story about the jack. I've been using a wheeled jack for years. It sure makes it easy for me to move the trailer around in my driveway. A few years ago I found that after I swung the wheel down, it would hold the trailer up but as soon as I tried to move it, the jack would start to collapse. Turns out that the nut end of one of the carriage bolts that holds the jack to the pivot plate had sheared off and the part that was left just barely caught. It was fine while in the vertical or horizontal position, but as soon as any lateral force was put on the bolt, it shifted just enough to move out of the pivot plate and cause the jack to collapse. You couldn't tell that the bolt was sheared unless you stood directly over the jack and looked down into the space where carriage bolts came out of the back of the pivot plate. It all looked good from the outside. It's now one of the things I check on a regular basis.
So, now, the only thing left to deal with are the lights. My only real concern is the brightness of the tail lights. Rewiring has long been on my list of things to do, but if an LED upgrade will improve the tai lights, I'll be satisfied for now. I've got an 900 mile round trip to my daughter's college in a couple of days and don't have time to rewire the trailer before then. If the LED's are brighter with the existing wiring, then they'll already be there when I get around to the rewire.
It's going to happen, I just can't say when.
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try running a wire directly from the tow vehicles battery ground to the trailers frame..... and the ground terminal of the plug....
if the lights get brighter then the ground is a issue and best fixed before you leave....
you could run a semi permanent ground wire for this trip till you fix it permanetely. some contact cleaner on all parts of the plug cant hurt.
taske a close look at the 2 parts contacts, they may be eroding away...
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On 8/18/2013 10:19 AM, bob haller wrote:

I spent some quality time with the trailer today and here's what I found.
First, the replacement 1157 LED bulbs didn't work very well. It's not that weren't they bright enough, the problem was the directionality. The socket inside the fixture is positioned such that the bulb "lays flat" as opposed to pointing straight out. The incandescent 1157 bulbs spread the light across the entire lens. The LED bulb acts more like a flashlight, only lighting up 1/4 of the lens in the direction it points. In fact, my wife thought the LED side was out until she stood directly behind the trailer. While the section that was lit was a little bit brighter than the incandescent, she said she would rather be following a trailer with the incandescent than the LED. I also tested it at night and about 3/4's of the lens was lit up, but there was still a dark void, unlike the incandescent who's lens was fully lit.
OK, so now I decided to look into the ground situation.
Just so you know what I'm working with, the trailer has the following set up:
- Six GE193 side markers, which are grounded via the screws that hold them into the trailer shell
- One GE193 license plate light, which is grounded via a pigtail to a self tapping screw into a trailer frame member.
- Two 1157 (dual filament) tail/blinker/stop lights. The left side is grounded via a pigtail to the same self tapping screw as the license plate light and the right side is grounded via a pigtail to a self tapping screw into a trailer frame member on the other side of the trailer.
- One 1156 (single filament) bulb for an interior light in a switched fixture which is grounded via a pigtail to the same self tapping screw as the right tail light.
The following tests were all done with the trailer disconnected from the tow vehicle hitch to eliminate the hitch connection from the equation. The only connection was the vehicle flat four to the trailer flat four. The vehicle flat four cable is attached to a factory installed connector in the vehicle's wiring harness and uses this cable and converter:
http://www.towready.com/content/products.aspx?lvl=3&parentid 00&catID05&part8336
When I started testing, I had removed the LED bulbs and the tail light sockets were empty. The side markers, license and interior bulbs were all installed.
The first thing I did was disconnect the ground wire that went from the trailer's flat four to the trailer's tongue, removing the trailer's frame as the ground. I ran a dedicated ground wire from the trailer's flat four to one of the rear tail light assemblies. When I turned the tow vehicle lights on, the voltage read 12.85 V at that tail light. Obviously, no lights came on because there was no bulb in the tail light socket and the rest of the lights had no ground.
I then ran a pigtail from the tail light's ground to the ground screw at the rear of the trailer that normally supplies the ground for that tail light and the license plate light. That screw goes into the frame of the trailer. When I did that, the side markers and license plate lights came on and the voltage at the tail light dropped to about 11 volts. When I inserted the tail light bulbs, the voltage dropped to the 9.5 V that I had been reading without the dedicated ground.
That tells me that whether I use a dedicated ground from the flat floor to the tail lights or use the frame as the ground path, I'm still going to get that voltage drop.
I then ran a dedicated ground directly from the battery's negative terminal to the tail light. There was no improvement. 12.85 volts with no bulb in the tail light socket and the rest of the trailer not grounded. As soon as I added a pigtail to the trailer frame, the voltage dropped almost 2 volts. Then when I put the tail light bulbs back in, I was down to the 9.5 level.
I went around the trailer pulling side marker bulbs and each time I pulled a bulb the voltage at the tail light went up by 0.2 - 0.5 volts. It was not consistent which tells me that each bulb was drawing a slightly different amount of current.
I think the next test is going to be to start running dedicated grounds to each fixture and see what happens. Since each fixture that uses the trailer frame as ground added to the voltage drop, there doesn't seem be a single cause for the drop, i.e. it's not one bad fixture causing the problem.
Heck, as long as I'm running all those grounds, I might as well just rewire the whole trailer. Running the extra ground wire to the side markers won't be that hard, but since the current ones are single wire fixtures with self tapping screws, I'll either need to use a nut, bolt and lug for the ground or replace the side markers with 2 wire fixtures.
I just wish I knew before I started rewiring whether or not a dedicated ground to each fixture is really going to resolve the voltage drop issue. Running a temporary ground wire is as much a pain as rewiring since there is really is no good way to attach the ground to the current side markers unless I make up bunch of clip leads and clip the ground to the ground bracket on the housing.
Maybe I should just do all my driving at night. The lights are easy enough to see when it's dark.
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On Sun, 18 Aug 2013 21:49:58 -0400, DerbyDad03

I doubt the ground is the problem, given the tests you have done. What is the voltage from the tail-light connection to ground when the lights are lit? If it is 9.5 volts, the problem is in the tow vehicle wiring. Use voltmeter from the connected trailer plug to the tail-light on the car. If over 1 volt (I like to see less than .2) the problem is in the trailer wiring connections. If voltage at the tow vehicle tail light is also low with the trailer connected it is a problem with the main tow vehicle wiring.

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...snip...

Please clarify what you mean by "use a voltmeter from the connected trailer plug to the tail light on the car".
From what pin on the trailer plug? To what on the tail light on the car?
And if the problem is with the tow vehicle wiring, what is the problem? What would I be looking for if the voltage you want me to check is over 1 volt?
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It's too late to work on anything now, but I wonder what would happen if I applied 12 volts from a fully charged battery pack like this...
http://britfa.gs/mph/src/133675951130.jpg
If I don't see a voltage drop with that, then it must be the tow vehicle, right?
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On Mon, 19 Aug 2013 04:52:46 +0000 (UTC), DerbyDad03

It would tell you if you had wiring trouble on the trailer. If it works from the pack, the trailer is A-OK - ready to go. Don't waste time on the trailer, look at the tow vehicle.
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DerbyDad03 wrote:

Hmm. Souns like a inadquate wire size or poor connections; crimping, screwed down with star washer, rust causing poor conductivity, etc. I don't know how old the trailer is. When I had my fiver, I used to inspect wiring at start of every camping season. if something is ??? I remedied it. And LED needs good diffuser lens, reflector to be effective. LEDs comein many different forms, shapes, specs.
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On Mon, 19 Aug 2013 04:42:33 +0000 (UTC), DerbyDad03

From the wire that feeds your taillights at the plug to any of your tail-lights on the tow vehicle. You want to do a "voltage drop" test. It will show if there is resistance between where the tow vehicle tailights get their power and where the trailer gets it's power - which boils down to the adapter wiring. If you have no voltage drop there, check the voltage from ground to the tow vehicle tail light - if the voltage is low there, you have bad wiring or a bad switch in the tow vehicle.
On MOST cars without a trailer towing package, you are smart to install a relay box (or electronic equivalent)) and feed it with a #6 wire from the battery (fused) and have the tail lights, signals, and brake lights on the trailer fed by the relays, and the relays turned on by the equivalent circuit on the tow vehicle. You can put the relay on the tow vehicle, or if you also run a live feed to the trailer, you can put it on the trailer (which means it is good for more than 1 vehicle, but any tow vehicle MUST have a live feed to the trailer)
Good idea also to have the live feed relayed so it is only on with the ignition to prevent power leakage and corrosion in the circuit - and having a switch so you can disconnect the power to the hitch is also a good idea (again, so nothing is live back there to encourage corrosion when not connected to the trailer)
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I assume that you want these readings taken without the trailer plugged in.
The reading is between 0.071 and 0.084 V. It varied each I started the van and varied from side to side.

I checked it using both grounds, the ground on the flat four and the ground at the bulb socket. 13.24 volts at the tail light using both grounds. 13.3 volts at the flat four plug using both grounds.
Resistance reading from tail light ground to flat four ground with the tail light bulb out reads 0.5 ohms.
Seems to me that the problem is in the trailer, correct?
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DerbyDad03 explained on 19/08/2013 :

You have just demonstrated why a lot of these after market lamp replacements, particularly LEDS are not certified for use on the road in most counties of the world.
On top of that at least some countries require WIRE ground connections back to the vehicle . The tow ball is not accepted as a connection.

I doubt adding wire grounds will fix the problem. As I see it you still have a single bad connection and every lamp you add increases the drop. You should be able to measure the drop across each connection (less than a volt) then one of them will be higer and you have got your culprit.
--
John G



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John G wrote:

Hi, Right on. Ohm's law. Poor connections in DC circuit act like a diode.
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