Trailer battery wiring questions?

[Tucson T4R]

...........................But the real reason you want to wire your trailer this way Robert is because...... I told you to.

And now we get down to the root of this equation. :shakin: :wings:

 

[Robert Bills]

:xxrotflma :xxrotflma :xxrotflma :xxrotflma :xxrotflma

But the real reason you want to wire your trailer this way Robert is because...... I told you to.

:hehe: :hehe:

 

[IH8RDS]

Martyn,
10 gauge wire, run from the battery to the center pin on the 7way should be good? My trailer is grounded because of the external lights. Do I need to only run a single hot line from the battery (fused of course) to the connector?

 

[Martyn]

Martyn,
10 gauge wire, run from the battery to the center pin on the 7way should be good? My trailer is grounded because of the external lights. Do I need to only run a single hot line from the battery (fused of course) to the connector?

The reason we run 10 gauge on the trailer side from the 7 pin to the battery is, it matches the 10 gauge that's typically run on the vehicle side to the 7 pin socket. So you want to match gauges.

The center pin on a 7 way is typically wired for auxiliary power, or back up lights. Check out the diagram here http://www.marksrv.com/wiring.htm for the location of the + .

The trailer body should be grounded to the chassis. When you ask "Do I need to only run a single hot line from the battery (fused of course) to the connector?" If you are saying from the battery to the 7 way plug, then the answer is yes. Put an in line 20 amp fuse in place.

 

[IH8RDS]

My Cherokee does not have the wire back to the trailer. So I will pick up a run of 10 gauge that will reach to the back from the vehicle battery.
Thanks

 

[Robert Bills]

Here's another source for trailer coupler wiring diagrams (although I used the http://MarksRV.com/wiring.htm diagram recommended by Martyn when I wired my trailer):

http://www.accessconnect.com/trailer_wiring_diagram.htm


7 Pole:

6 Pole:

4 Pole:

 

[IH8RDS]

I currently have this on my bumper. Just wired for turn signals and stop. Basic wiring.

Am I right to say the center pin will be the power?

 

[Robert Bills]

My Cherokee does not have the wire back to the trailer. So I will pick up a run of 10 gauge that will reach to the back from the vehicle battery.

Are you going to use a constant duty solenoid (as pictured by Joanne) or go direct from battery to trailer connector? I highly recommend the former.

The hardest part of the project will be to determine the appropriate "ignition hot" wire under the hood to tap for the trigger wire to the solenoid. I don't know which color wire in the bundle through the firewall on a Cherokee, but someone here probably does. A simple test light will confirm it. Also, be sure that you insulate the 10 ga. wire from solenoid to trailer connector anyplace where vibration, etc. could cause wearing. You do not want any contact between bare wire and your tow rig!

 

[Robert Bills]

I currently have this on my bumper. Just wired for turn signals and stop. Basic wiring.

Am I right to say the center pin will be the power?

No. You have a 7-way connector. Although some trailer guys do wire 12v for their trailer battery through the center pin (or sometimes the ground), the standard is to use "Pin 4" as noted the following image. The center pin in a 7-way connector is normally used for auxilliary or back up lights on the trailer.

That being said, you can use any pin you like in your connector so long as your tow rig and trailer are wired the same. Just be aware that if you stray from "normal" wiring, your tow rig wiring will not match the trailer wiring on anyone else's trailer, which will have interesting if not disasterous results.

 

[Martyn]

Here's another source for trailer coupler wiring diagrams (although I used the http://MarksRV.com/wiring.htm diagram recommended by Martyn when I wired my trailer):

http://www.accessconnect.com/trailer_wiring_diagram.htm

Robert

That is a much nicer diagram.

I would suggest that instead of wiring the cable from the 7 pin socket directly into the trailer wiring harness that a junction box be used. If there are electrical problems then it's a great place to start from.

 

[Robert Bills]

I would suggest that instead of wiring the cable from the 7 pin socket directly into the trailer wiring harness that a junction box be used. If there are electrical problems then it's a great place to start from.

That is a great idea. Much easier to trace a problem from a junction box than at the socket or by pushing probes into the wires. One of my "when I get around to it" projects is to fit a waterproof junction box into the "C channel" on my trailer tongue so that I can access each wire from there. Haven't found the right box yet, but I know there's one out there.

 

[ntsqd]

FWIW I've seen Tuperware containers modified for that and similar uses.

 

[IH8RDS]

No. You have a 7-way connector. Although some trailer guys do wire 12v for their trailer battery through the center pin (or sometimes the ground), the standard is to use "Pin 4" as noted the following image. The center pin in a 7-way connector is normally used for auxilliary or back up lights on the trailer.

That being said, you can use any pin you like in your connector so long as your tow rig and trailer are wired the same. Just be aware that if you stray from "normal" wiring, your tow rig wiring will not match the trailer wiring on anyone else's trailer, which will have interesting if not disasterous results.

Thanks for the clarification. I definatly want it standard because of the use of two different vehicles.

 

[Martyn]

That is a great idea. Much easier to trace a problem from a junction box than at the socket or by pushing probes into the wires. One of my "when I get around to it" projects is to fit a waterproof junction box into the "C channel" on my trailer tongue so that I can access each wire from there. Haven't found the right box yet, but I know there's one out there.

The 7 pole junction boxes are very generic, you can find them by doing a search. We use one similar to the picture attached.

 

[Robert Bills]

The 7 pole junction boxes are very generic, you can find them by doing a search. We use one similar to the picture attached.

I like that box. It looks perfect. Is there a local supplier? (Orange County or Inland Empire - my dad still lives in Claremont and I go there often.)

Otherwise, I'll try Google, but that is sometimes hit or miss.