7-Way connector-alternate power location

[vernj4]

The goal: have a 12v source of power in the bed of the pickup. This would be used to power a 120 volt compressor via a 400 watt invertor.

Needed hardware: besides the inverter, a trailer plug with a 6-8 ft power cord would be made using 12 ga stranded wire. Ring terminals would be applied to the ends of the wires.

The question: Would the Black (+) and white ground (-) be available and supply 12 volts through the 7-way connector?

[a5150nut]

Looks like it to me - see diagram http://www.a1warriortrailers.com/hitches/7pin-diagram.jpg

[JohnC]

There is a 40 amp feed in the trailer plug. I'm not sure the colors are correct, though.

What kind of compressor do you hope to run off a 400 watt inverter?

[vernj4]

1-the big black wire should be the 12 volt source.
2-have a small 100 psi compressor that pulls 2 amps; enough to top off tires, when needed.

The question; if I put a load across the black and white wire, will I have access to the 12 volt power? If so, is the power available all the time? Key on? key off?

[JohnC]

Someone else will know for sure, but on the '06 I had to install the 40 amp fuse to activate the circuit. It is always on. You're going to need all 40 amps... I'd go bigger than #12 wire; #8 sounds about right.

Before you spend a lot of time and money, make sure the inverter has enough juice to start the compressor when it has pressure in the tank. (Whatever the kick in pressure is, say 80 psi. Starting empty is easy...)

[DmaxMaverick]

I agree with John. You'll need to accommodate for all 40 amps available, and 8 ga wire would be recommended, 10 ga at a very minimum. Your 2 amps AC will be about 20 amps DC, not considering starting current, which can easily be double. Any good inverter will accommodate around a 150% burst for motor starting, but this is usually limited to only a couple seconds. Take into consideration the inverter's overhead (usually 20%, or more), and the wire length impedance, and you can easily eat up every bit of the 40 amps available on that circuit. Also, it should be hot, engine on or off, key on or off.

Do not try to use the cig lighter or power point for the inverter/compressor. It will easily overload that circuit, and burn fuses (if you're lucky, it won't burn wires, it's only rated/protected at 15 amps).

You would be better off connecting the inverter directly to the battery (alligator clips on a short wire), and use an AC extension cord or longer hose to reach the tires. The shorter distance of DC wiring will provide greater AC power downstream. The wire run impedance is significantly less at AC volts (revisit Edison vs. Westinghouse/Tesla).

[vernj4]

The black wire marked "Battery Charge". When a meter used to check.....no power is measured. Does this mean a battery must be installed.....so the circuit can sense the batery voltage and charge accordingly?

[DmaxMaverick]

No. It's a dumb circuit. You probably need to install the fuse for the charge circuit (they don't come with one installed). It's in the underhood fuse box.

[vernj4]

Finally got things sorted out......the biggest problem was the 40 amp fuse had not been installed......hence the black lead/battery terminal/located at 11 o'clock(aft looking forward into the connector) was deader than a door nail!

I understand and totally agree that the 12 ga wire is marginal at best (for this application). Theoretically, 12 ga handles 20 amps whereas an 8 ga handles 40 amps.

The big problem would be how to run a GOOD quality 8 ga (or even a 6 ga stranded wire) from the fuse box to the 7-way connector
1) got to protect the wire from abrasion and heat
2) how to get a good connecttion (sealed from the enviroment) at the 7-way

Indeed, opening the hood and using alligator clips to connect to the battery is looking more and more like the best solution...............

[DmaxMaverick]

It depends on how often you intend on needing it. If it isn't very often, a little inconvenience (opening hood) may be the better option. I need the same thing on occasion. I use a B&D Air Station with the RV (hardwired inverter), or my onboard 12V air bag compressor. If you will use it more often, an onboard compressor may be less headache, in the long run.