Trailer Light Grounding

[Soundguy]

i like an ammeter on a tractor.. not a voltmeter. shows a more clear picture of charge system health, especially battery. easy to see a bad cell with excessive current draw far after start current should have been replenished... ( both would be nice.. but if I can only have 1, then an ammter. Heck.. an idiot lamp is better than an ammeter.. at least you know you are at a discharge.. whereas.. on a voltmeter.. it may be a slight discharge.. and depending on gauge resoloution.. you may not know till it gets to 10-11v.. IE.. WAY discharged for a lead acid storage battery..

 

[downslope]

Heck.. an idiot lamp is better than an ammeter.. at least you know you are at a discharge.. whereas.. ..

You mean better than a voltmeter, right?

 

[downslope]

Had a bad ground on my 12 ft landscape trailer a few years back. the poor ground backfed the lighting circuit and fried the radio, antilock brake module, and blew the backup light fuse. (backup light circuit terminated at truck and doesn't even go to the trailer). I rewired the trailer and ran a ground wire from all the lights back to the plug.

I'm trying to understand how a bad ground on the trailer could cause all that damage. Did you replace the plug at the same time you rewired? If it was a seven-way plug maybe something in the plug was shorted or wired incorrect. I mention the seven-way because I believe they have a pin for backup light, even though it wasn't (or shouldn't) being used on the trailer side, and that would have fed to the backup circuit in the truck if the truck had a factory trailer connector.

 

[SandburRanch]

I had a snowmobile/dump type trailer once that I had a real crazy light problem with. Even though I had a good strong 13 volts (Hummmm no load....) at all of the sockets ..... the bulbs would not light. After some serious head scratching I figured out that where the frame hinges for the dump was not carrying any CURRENT to fire the bulbs. I put a jumper from the tongue to the rest of the frame around the hinge and I had lights.

Lesson: Run a seperate ground. Also, get LED lights and never worry about corroded sockets again.

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A tilt boat trailer with the ground wire attached to the wrong trailer half can also make a person scratch his head and other body parts for an hour at least until he finally sees the light.:confused2:

 

[RandyT]

I'm trying to understand how a bad ground on the trailer could cause all that damage. Did you replace the plug at the same time you rewired? If it was a seven-way plug maybe something in the plug was shorted or wired incorrect. I mention the seven-way because I believe they have a pin for backup light, even though it wasn't (or shouldn't) being used on the trailer side, and that would have fed to the backup circuit in the truck if the truck had a factory trailer connector.

This all happens about 2 years after is was bought new at a discount price from TSC since it was 2 years old at the time. It has the flat 4 pin connector with ground going to jack bolt at the time of failure. Due to the poor ground I think that it was using the tail light circuit on the trailer to backfeed the system when I used the turn signals (clock on radio would flash with the turn signal). The backup lights, ABS module, and radio are on the same fuse. When it blew the fuse it caused a voltage spike in the system.

Since then it has been replaced with LED lights, new wiring harness, and soldered and shrink tubing to seal all connections. since the LED's has a separate ground wire unlike the Peterson bulb lights that were factory installed I ran a ground wire to all the lights and hooked directly to trailer plug. would have ran ground wire to light ground even it didn't.

 

[Soundguy]

You mean better than a voltmeter, right?

yep.. my bad.. ammeter is my fav, then idiot lamp.. then voltmenter, if I can only have 1. sometimes I got all 3 .. etc..

good catch.

holidays are rough .. can't even think straight half the time,.

thanks

soundguy

 

[gengine]

Are ya gettin 12v at the vehicle plug? The next thing is using the ohm meter. Light bulbs are resistors, so you will have resistance there, but just a little. Most trailer lights are grounded to the frame just inches from the light. So, checking each terminal to the trailer frame should show resistance, but that could be read two ways. If there is high resistance, there is a problem with that circuit. If there is resistance, through the light bulb, then the circuit is complete. With no bulb, there is a break in the circuit. If there is not resistance, there is a short in the circuit. Most trailers also have a ground wire bolted to the tongue going right to the plug. That way the trailer is grounded to the plug as well as the through the hitch. Good luck, hope I helped a little bit.

 

[downslope]

Are ya gettin 12v at the vehicle plug? The next thing is using the ohm meter. Light bulbs are resistors, so you will have resistance there, but just a little. Most trailer lights are grounded to the frame just inches from the light. So, checking each terminal to the trailer frame should show resistance, but that could be read two ways. If there is high resistance, there is a problem with that circuit. If there is resistance, through the light bulb, then the circuit is complete. With no bulb, there is a break in the circuit. If there is not resistance, there is a short in the circuit. Most trailers also have a ground wire bolted to the tongue going right to the plug. That way the trailer is grounded to the plug as well as the through the hitch. Good luck, hope I helped a little bit.

Also, sometimes what can happen is one stoplight has a good ground to the frame and the other one doesn't. So when you step on the brake the current passes thru the first light and then through the second one to ground, the lights are in fact in series and will be dim. The same thing can happen with the tail light circuit when only one hot wire is run back to service both sides and one light has a poor ground.

 

[theburren]

Hello-- this is my first post~ I have an old (1991) diesel pusher, which I've been slowly fixing up.. I just installed some 4" round TruckLite LEDs in the back as Stop/ Turn indicators, since the taillights it came with are barely visible. I notice that there is a little bit of overlap (for lack of the proper word) on the passenger turn signal when I use the driver side signal, and vice versa.. Its very subtle-- a slight blinking on the non-blinking side....

Anyway, I also just finished wiring my 1996 Toyota truck so it can be flat towed behind the bus. I'm using a RoadMaster Tow Bar. I decided to wire my Toyota to act like a trailer, so I didn't have to worry about magnetic lights, etc.

The Diesel bus is a combined Turn/ Brake system, and the Toyota is separate. So I ran Left, Right, Tail, and Ground wires from the back of the Motorhome to a 4 wire socket adapter, which I connect via a coiled cable to another 4-wire socket mounted on the front of the Toyota. I grounded the Toad directly to the negative battery using a piece of solid copper wire, and run Left, Right, and tail light wires to the rear, where I use 4 diodes to prevent backfeeding --

My problem is this: the lights on the Toyota are dim compared to when its not being towed. The overlap issue with the signals is also more pronounced, making it look almost as if Im using flashers instead of a turn signal.
And when I step on the brakes, the trailer lights (Toyota) first go dim then get brighter.

Is it possible that this is a poor ground FROM the towing vehicle? Its an older bus, and the wiring in the back is not the most organized. I really need to fix this, since I'm worried about safety when driving at night.

Should I run a dedicated ground from the Motorhome's negative battery terminal and combine it with the existing ground, which is already going to the 4-wire socket adapter? Is it possible I need a heavier duty flasher unit? I think mine is already heavy duty... 25 amps.. or is it probably a faulty groundwire in the bus.

Sorry for the long-winded question-- And thanks in advance for any help--

 

[Soundguy]

2 sugestions I have for you.

1, a seperate aux ground NEVER hurts, and cures many DIM lamp problems, and pulseing or blinking lmap problems.

2, they make a brake / turn signal adapter for units that have combined hooked to non combined units.. etc.

here's a bonus: 3, if the wireing is bad at the back of the buss... rewire. bad wirees, insuficient size, and bad conenctions make for dim lamps.. especially since you are making a train with extra connections..

soundguy