trailer lights... part 2

[Bryan]

okay here's the update. I ended up taking out the converter, and added an extra set of lights to the trailer. Now everything works great!!! I do have one question though. If you remember my original problem was low voltage therefore I ran new wire from side driver panel junction all the way to the rear tail lights. It increased my voltage by 2 volts and made the lights a lot brighter and also enough to light up the whole trailer. But here is something I'm still noticing. I'm not getting the same amount of voltage on the lights as I am from the battery. In other words, if I test on the battery terminals and I then I test on the lights, I'm still missing about a volt. Another thing I have noticed is if I test the hot side of the "marker" switch at the driver panel with lights off, I get full voltage, but as soon as I turn the switch on, it drops about a half of a volt on the hot side of the switch. I'm told by some truck driving mechanics that I should be getting the same voltage everywhere weather it's at the dash on in the tail lights themselves. Any ideas?

[Nusa]

Now check the voltage at the battery when you turn the lights on. I bet you'll see a change there as well. You're adding a load on the battery without a charging system in operation.
Start the bus or put a charger on the battery if you want a stable reference voltage that doesn't react to load.

[Seangie]

Brian -  depending on the gauge of the wire you ran to the back you will get a voltage drop.  This could be anywhere from .1 volt to a whole volt if the wire is thin enough. The thinner the wire the bigger the voltage drop. Here is a neat calculator for that - http://www.calculator.net/voltage-drop-calculator.html

-Sean

Fulltiming somewhere in the USA
1984 Eagle 10S
www.herdofturtles.org

[Bryan]

new update... I did some tests while the bus was running. Like you said the voltage at the switch matches the battery when the marker lights are off. When running, the battery terminals and the switch both were at 14.1 volts. When I turn the marker lights on, it ALSO matches the battery but there is a drop. At the switch and at the battery it is 13.6 volts.

Just incase that didn't make sense...
Bus running at fast idle - Marker lights OFF - Switch = 14.1 volts
Bus running at fast idle - Marker lights OFF - Battery Terminals = 14.1 volts
Bus running at fast idle - Marker lights ON - Switch = 13.6 volts
Bus running at fast idle - Marker lights ON - Battery Terminals = 13.6 volts

I ran 12 gauge wire which I've been told was more than enough. And when I say I ran new wires, I simply ran them from the side driver panel junction box, all the way to the rear lights, I didn't rewire all the markers themselves and I also didn't rewire from the battery to the junction panel. But rewiring the parts I did increased the voltage to the tail lights by almost 2 volts.

What are you guys thoughts on this? Thanks!!! 

[gumpy]

I ran 12 gauge wire which I've been told was more than enough.

That depends what the current load is. How many lights you are powering with that 12ga wire?

12ga is good for about 18 amps.

[Bryan]

There are only 4 lights running on the 12gauge wire (the tail lights)... All the markers are run like they were when we bought this bus. My marker switch also turns on the tail lights. 😃

[Bryan]

In other words we didn't change anything about the marker wires. We just added a new wire for the tail lights in particular.