Missing 12v to trailer being towed

[dshogman]

In hooking up a 7 way plug for my new trailer, we found out that there was no 12v to the black wire in the old plug. So we set up the 7 way plug with no 12v to charge the breakaway battery.
Has anyone come across this problem? We thought it might be a fuse somewhere. If not that and barring any issue with Vansco, where would be a good place to get 12v back there to run to the black wire of the receptacle?
Thanks.

[bigskymt]

You might only have 12vdc to that wire with the ignition on.

[dgerstel]

Try this post:

Tow Wiring and Extra Wires

[Paul R. Haller]

In every tow vehicle I have ever owned I have upgraded the 12 volts to the trailer tow plug. I run a # 10 black or red wire from the alternator output post through a large 25 amp fuse to one pole of a solenoid screwed to the firewall. On the other side of the solenoid another black(or red) #10 wire from there all the way back to the +12 volts at the 7 way plug. The original+12 wire there I cap off. Now find switched + 12 volts from the ignition and wire that to the trigger of the solenoid. Finally I find a good ground and using a # 10 wire run that up to - 12 volts at the 7 way plug. Most tow vehicles have a # 16 wire for that line and many manufacturers don't have a heavy duty relay there either. Once you do this, your 7 way plug will more easily charge the trailer batteries and not limit current or voltage by using a small wire for charging. remember to also uprate the ground wire too.
The capped off +12 volts I always use to power up a pair of 55 watt halogen back up lights, through a relay of course, so I can see while hooking up. I use the same process for hooking up back up lights for the towed vehicle. On my current 5er I have 3 sets of 55 watt halogens for backing up using the existing back up lights as a trigger for 3 relays to power up lights on the trailer all wired to the trailer batteries so I can see back there at night rather then trying to see using the sparrow fart lights the manufacturer provided. I run the lights on either side of the trailer at about 8 feet back from the front and one set in the middle of the trailer and another set beneath the rear bumper.
As for trouble shooting the charge circuit, just get a VOM and trace out the wire. Most have a fuse somewereand some others also have a relay too.
-Paul R. Haller

[dshogman]

Thanks Dale for the reference. In that thread, your post #13, answering the question about the 12v to the receptacle, you say it's through the Vansco acting as a circuit breaker. So if i have no 12v at the receptacle, is there any way I can get the Vansco to supply that 12v?

[Old Scout]

Read on, Vansco has limited capacity to provide electrical power beyond the "typical" automotive uses [ie coach turn signals/stop lights, etc]. Need to use relays or direct connects to your chassis batteries to power trailers and/or high power lights, etc......

[takepride]

Quote:

Originally Posted by Paul R. Haller sparrow fart lights

I gotta remember that one!

David:

It is easier and low tech, but I would run a cable from you chassis batteries to a 20-25 amp self-resetting circuit breaker then to the umbilical cord. At the towed, run from this connection to another self-resetting circuit breaker and then to the battery. Let your alternator just continue to charge the coach batteries without adding another load/potential problem.

I've done this to both my toads. Works great. Also recommended by built-in supplemental braking manufacturers to eliminated dead-toad-disease.

[dshogman]

OK takepride, I see what you're doing. Except for the 2nd self-resetting circuit breaker on the trailer. Why is this needed if there is already one behind the receptacle on the coach?
Thanks.

[takepride]

David:

Destruction limitation. Power runs both ways. One protects in sending juice to the toad, the other in case there is a reversal of power and you don't want to fry your plugs and umbilical. There is also the issue of somehow sending power from the plug or umbilical into your toad, via something other than your coach batteries. Lightning, someone playing around with your plug, untrained service techs, dropped tools, short at the plug.......