On the 7 way (std connector nowadays) is the +12 constant connected from the factory, or do I need to add it in?

Second, what gauge wire feeds it? #10 or #12?

I'm wanting to run the cooling blower for the drag car (Torque Convertor) from this wire. The blower pulls 5 amps @ 12VDC (230 CFM on a 4" tube), so I figure #10 wire would be required for the entire run from the truck battery to the 7-way, then from the 7 way to a socket on side of trailer.

What is a good socket/plug design to put on the side of the trailer, that won't corrode over winter? Everything I see only goes up to 14 GA or so. Closest I found was a "watertight" marine cig lighter type socket (cheesy), or a trolling motor socket ($$$). Seems like even a 4-way or 7-way standard trailer connector would be cheaper, but then i fear it wouldn't be idiot proof (if we ever sold the trailer...doubtful). And I dont think the 4-ways come in 10GA. I'm thinking something like banana plugs or down that line. Something simple, solid, preferably non-reversable, and idiot proof.

If I put 3 sockets on the trailer- one left, one right, and one on back- I would have to ground all of them at the tongue, correct?

Here's the blower, Attwood 1747-4 http://www.attwoodmarine.com/store/p.../turbo-4000-ii

 

I would certainly run a main and dedicated wire from the battery but Im not sure if I would tap it into the 7 pin connector at all. I would be inclined to keep it separate and add another quick disconnect harness like you are talking about.

Even though a #10 wire for 5A should be sufficient, watch out for voltage drops on such a long wire. All sockets would have to complete their circuit by being wired to the trailers frame or tongue.

 

WOW... #10 wire sounds very, very big for 60W (12V @ 5A). I recently did a power supply design that had #10 wire on the output for ~600W and the wire barely got warm at full military power.

#10 gauge can take 30, 35 or 40 A continuous depending on the temperature rise you can allow for. The application I used it for was @ 28V at about 21 to 22A.
http://en.wikipedia.org/wiki/American_wire_gauge

You will need to have power and ground at each receptacle location, but be wary of creating ground loops. I would recommend a single ground point at the tongue that connects up to your truck then a wire to each receptacle on the trailer. Do not daisy chain the ground. If you don't care about creating noise on your power bus then you can do just about anything with the grounds. However, since your truck has more electronic processing power than all of the Apollo shots combined, you care very much about not creating noise on the power bus on your truck with that 60 W fan motor. You may even want to look into an isolation transformer to knock down the fan noise.

As always, this is just my $0.02 and YMMV.

 

^^^^ LOL ....nice

 

I do not know if the +12V is wired into the 7 way by default. I guess it depends on who put it in (whether stock or aftermarket). Easy to check though.

http://www.etrailer.com/faq-wiring.aspx

 

My factory 7way has the 12V in it. (2004 ram 1500) It charged my RV battery from dead on a 1 hour drive home after I picked it up from the dealership service dept. Probably not full charge, but the gauges in the RV aren't much good for anything but showing a charge is present.
That being said, I heard (unconfirmed) on an RV forum that it may also be switch relayed from the ignition so that it breaks the connection when the truck isn't running. I never really cared to check it out myself since I usually unplug the trailer from the truck if I am going to be sitting more than a couple hours (like an overnight sleep stop).

As for connectors in the trailer, you could go to an electronics supply place, or an equipment dealership (tractors, excavator etc) and see if you can pick up some rugged connectors. Once you wire it correctly, only that type connector will go in, and only in the correct way. Also, you could label your connectors as with a sticker on the wall showing + and - contacts as well as Voltage so other people will know what the socket is.

Hope those are helpful suggestions.

 

On my '04, my seven wire plug keeps it's 12v constant all the time.
I built a 7-wire plug to female cig lighter adapter so I can plug my beach toy inflater in at the rear bumper as well as my 12v compressor for airing up my helper springs.

It never shuts off.

 

It was a stock wiring, so I figure it's there...I also figure that dodge probably tried to cheap out with #14 wire. I just checked the haynes for my Dako, and it doesn't specify a different wire size for the factory 7-way, just says red/white straight to a 20 amp fuse. Obviously the fuse is over-rated for the lead.

edit- just ran out and checked- got red, white, yellow, green, and blue. I didn't see a violet, orange, or black, but they may have been hidden in the bundle. All the same diameter- #16 or #14 it looked like. Wayy too much Vdroop for a 5 amp inductive load. At the same time, the fuse for it in the box is 20 amps, but no way that wire could sustain 20 amps @ 12VDC as long as it is- that'd be over 1.5 volts of Vdroop.

FYI, this is a flat-deck trailer, not enclosed. That's why the connectors need to be weatherproof, I'd be mounting them under the edges, and it lives at the storage lot.

 

Check out http://circuitcalculator.com/wordpre...er-calculator/

It's a wire parameter calculator. Take a guess at wire size (you had 10AWG) , input what you think the max temperature the wire will see in the engine compartment (200F??), the wire length and number of bundled wires (1 in your case, unless you add it to an existing loom of wires)

Focus on the ampacity in the results, and I personally shoot for 1.5x to 2x the max amps you want to run (5A in your case) If you are using a low quality insulation on the wire, I would stick with 2x.

Just change the AWG until you get an ampacity about 2x of the max you want to run.

 

That link claims I can go to 16 guage- probably what the truck is wired with?

Using the calculator at the bottom of http://www.powerstream.com/Wire_Size.htm using 16 guage, there's a 2.6 volt drop on a 40 foot run (figure 13 feet of truck, and 27 feet of trailer to the very back connector). It's only a 0.6 volt top for #10 wire, and only 1 volt for #12.

The other choice, is that we always have to run the generator to run an electric leaf blower.

wire cost (1 time) versus gasoline cost for generator (times 26 races a year.......)

or run the fan off of the car batteries....

I think the wire is cheaper. And the car needs both batteries (optima reds) to start, we found that out the hard way when we disconnected one cheaking for a gremlin. The radiator fans and water pump pull enough amperage, not sure that we need to add an extra fan onto that...

The goal is to not have to rely on the generator (an thus it costs less long term)


At the local track, we can park the car next to the trailer- I'd just put a plug on the tongue of the trailer, and wire is a non-issue. But at a track that's a little further away, you have to park the car behind the trailer- thus having to mount a plug at the back of the trailer. That's an extra 27 feet of trailer (22 ft bed and 5 ft tongue) that has to have wire ran.