More about what the check lights mean from Mike Sokul.
Open Ground: The outlet has no ground connection, which can easily allow your RV or electrical appliance to develop a hot-skin voltage. DO NOT plug into this outlet.
Open Neutral: This means that you have no operational appliances, however, they’re actually energized with 120 volts and can be dangerous if you open up an access panel and poke around inside while the appliance is plugged in. Never assume anything is electrically safe to work on unless it’s unplugged.
Open Hot: This means you have no power in the outlet at all, likely from a circuit breaker being tripped or turned off.
Reversed Hot and Ground: Even though your appliances won’t operate, their chassis will be energized with 120 volts, which is extremely dangerous. DO NOT plug into this outlet. EVER!
Reversed Hot and Neutral: Unless something else is miswired, this in not immediately dangerous and won’t cause a hot-skin condition by itself. Use with extreme caution.
Correct Wiring: This means the outlet is safe unless you have a rare miswiring condition I’ve named an RPBG (Reverse Polarity Bootleg Ground), in which case everything will operate normally but there will also be a hot-skin voltage. That’s why I suggest you also use a Non-Contact Voltage Tester to confirm there’s no hot-skin voltage after plugging in.
The 12volt Side of Life (Part 1 & 2) – A great reference particularly about batteries and trailer electrical systems including solar. Part 1 at http://www.marxrv.com/12volt/12volt.htm; Part 2.
The reference for all things RV Electric is http://www.myrv.us/electric/
http://www.timberman.com/ELECTRIC/electric.htm – Last updated 2005 but still a lot of good info. Recommended and linked from myrv.us as of 2018.
Mike Sokul’s Articles
7-pin and 4 pin hitch wiring diagram
TRAILER CONNECTOR WIRING SCHEMATICS – 4, 6, & 7 PIN TRAILER CONNECTOR WIRING PINOUT DIAGRAMS
Voltage drop for AC– what’s acceptable?
You can poke the VoltAlert into the tall neutral slot (no blink or beep), then the ground hole (no blink or beep) and finally the shorter hot slot (should blink and beep). It won’t tell you the exact voltage of the outlet like a voltmeter, but it will confirm if the polarity is correct and tell you if the ground connection has been floated and electrified by another RV with a short in its own wiring.
Volts, Amps, & Watts
From http://www.rv-dreams.com/rv-electrical.html where there is a lot more and worth looking at again. Good info on solar panels.
Watts are a measure of electrical power. Amps (or amperes) are a measure of electrical current or flow rate/volume. Volts are a measure of force or pressure through an electrical circuit.
Let’s go back to our water pipe analogy. As I said before, Volts are like water pressure. Amps are like the water flow rate. Watts are then like the total water output produced by the combination of water pressure and flow.
Now for the math I promised earlier.
Watts = Volts X Amps
So, electrical power is determined by the amount of electrical current (amps) and the amount of force (volts) used to push that current. The higher the force (volts) or the higher the current (amps), the more power (watts) there is in an electrical circuit.
Doing a little algebra, we get this equation:
Amps = Watts / Volts
Why do we care?
We care because we have to determine how much electricity we need to run the goodies in our RV. These math problems help in figuring out what our batteries can do, what appliances we can run at the same time in various situations, and what future upgrades to the electrical system we might want to undertake.
We usually need to know amps since most of our RV electrical knowledge is based on amps. We plug into 20-amp, 30-amp, and 50-amp electricity sources.
We always know volts. It’s either 120 or 12 for RVs depending on whether we are talking AC (120-volt) or DC (12-volt).
And wattage is usually available. It’s located on the appliance nameplates or in the owner’s manuals. Or, wattage can be estimated by using the many online wattage tables for common RV appliances. Of course, if you use online tables, remember they are just estimates as your actual appliances may vary.
Testing The Rv Park Powerbox, Without Being An Electrician
https://www.youtube.com/channel/UClL6nv20w_QQL-SeSLpwv8g