MICTUNING Heavy Duty 7 Gang Junction Box Install Help

[Yoda]

Keith installed backup lights, so he may be using that yellow wire? It's been awhile, but this thread has info (I didn't read the whole thing): https://gdrvowners.com/forum/operati...lights-install

Good idea, though, for most of use about using both posts!

Howard

Scott'n'Wendy

Scott - Howard is correct, yellow wire is in use, but great idea. I was assembling the parts to do this yesterday , then got thinking I have several step down connectors (heat shrink) where I could combine two wires to one outside the box that would reduce the number. Size will probably increase - 2-#14 to 1#10. Ill know more tomorrow. Today is battery maintenance, final wheel lug nut torquing, and test drive. Then driveway and work space clean up.

I also need to read up on my trucks available brake settings again - too many screens and buttons to push

Good information and brainstorming everyone.

Keith

[Scott'n'Wendy]

then got thinking I have several step down connectors (heat shrink) where I could combine two wires to one outside the box that would reduce the number.

If it were me I'd just put all seven on one stud then. There is enough stud there and it sure beats a wire nut. I have 5 on my white stud now.

[Cate&Rob]

x2 on Scott'n'Wendy Scott’s advice to use a single stud for all ground connections. This is easy to do. A long bolt through a hole in the frame secured with a serrated nut and then all the ground terminals secured with another nut. Way more secure than any combination that includes wire nuts.

Rob

[Yoda]

x2 on Scott'n'Wendy Scott’s advice to use a single stud for all ground connections. This is easy to do. A long bolt through a hole in the frame secured with a serrated nut and then all the ground terminals secured with another nut. Way more secure than any combination that includes wire nuts.

Rob

Scott'n'Wendy

So Rob are you saying add a frame stud and tie everything there? The OEM box negative returns are not grounded to the frame at that location that I know of, just tied to the negative return in the 7 pin cable. They all appear to be the negative returns from the trailer lights, so maybe should be isolated from the trailer and just grounded to the truck through the 7 pin.. Even withe box wiring being insulated (plastic box) should I add a frame ground to it?

I hope I said it correctly

Thanks Keith

[Jlawles2]

Keith,

From what I could tell, one of the wires runs back to the mass ground point in the front bay. I believe you have already addressed this massive cluster and converted to something better. You (i can also) can check for continuity between the 7 way ground and the frame by using the diode or continuity tester on your meter. I Believe this is why they say to disconnect the ground in the 7 way when installing the DC-DC charger.

[Cate&Rob]

Yoda
I was agreeing with the advice that ring terminals on a stud is a far better plan the clusters of ground wires in a wire nut. I don’t see anything wrong with grounding everything 12V on the trailer to the trailer frame and then electrically connecting the trailer frame to the truck chassis through the 7 pin cable ground wire. Unless, you are running a DC/DC charger where the current would require a much larger wire than what is in the 7 pin.

Rob

[Scott'n'Wendy]

so maybe should be isolated from the trailer and just grounded to the truck through the 7 pin.. Even withe box wiring being insulated (plastic box) should I add a frame ground to it?

I hope I said it correctly

Thanks Keith

Those white wires are bonded to the trailer frame anyway, just not at the kingpin.
And 'no' on trying to ground the plastic box.

[Jlawles2]

I guess if someone wanted to be extra safe with a DC/DC charger system, they could install a fuse on the ground wire between the truck and the frame of the trailer. This Fuse would need to be monitored to ensure it does not blow causing the trailer lights to not work.


I don't know enough about the DC/DC chargers to determine if the charger is "isolated" on the input to output sides on the negative. If it were, then the MFG would not suggest disconnecting the 7 way ground. This to me poses a problem that if the DC/DC system is not connected, then you do not have trailer lights. I guess it would be possible to install a DPST relay and use the NC side of the relay to control the ground from the truck. When power is applied to the DC/DC charge system the relay is energized and OPENS the contacts thus killing the truck whip cord ground to eliminate overloading of that circuit.

[Yoda]

Yoda
I was agreeing with the advice that ring terminals on a stud is a far better plan the clusters of ground wires in a wire nut. I don’t see anything wrong with grounding everything 12V on the trailer to the trailer frame and then electrically connecting the trailer frame to the truck chassis through the 7 pin cable ground wire. Unless, you are running a DC/DC charger where the current would require a much larger wire than what is in the 7 pin.

Rob

I am running a DC-DC. Its 60A limited to 30A. Its on my Flooded batterys. It has a separate negative return (2awg) back to the truck battery. From what I know I am good until I switch over to Lithium. However I am still not quiet understanding the need to disconnect it as the truck charging system has protection built in and operates at the same voltages or close. Its been operating fine sence the install.

Scott'n'Wendy

Scott I am going to find out if they are bonded back to the trailer frame somewhere else as Joseph mentioned Jlawles2 . Right now I see no evidence of that but will be checking. Part of my fun today. The wire count appears to matche what would be needed for the exterior trailer lights, stop, turn, clearance and brakes assuming GD home run everything as I am finding elsewhere.. My new Klein meter showed up yesterday so it will be fun to learn how to use it doing this. As everything works now I am holding off on the new junction box install until I get the road test done

Keith

[howson]

However I am still not quiet understanding the need to disconnect it as the truck charging system has protection built in and operates at the same voltages or close.

Disconnect "it"? What, exactly, do you feel necessary to disconnect?

[Jlawles2]

Disconnect "it"? What, exactly, do you feel necessary to disconnect?

Howard, It's a giant CYA of the DC-DC system MFG should the charger loose ground and try to use the 7 way ground that is not designed to carry the 30 plus amps that will be required by the charger. Should the charger loose it's primary ground, the current returning through the whip cord and truck wiring COULD POTENTIALLY CAUSE AN OVERHEATING and result in everything bad you can think of.

[Lonestar]

Great thread. I don't think it's been mentioned, but instead of using the kit mentioned in post #1, is there any reason not to use the existing 7 wire cable and just go with the junction box?

https://www.amazon.com/MICTUNING-Way.../dp/B07QDQRX7P

Also, is anyone soldering the ring terminals instead of crimping?

[Country Campers]

Lonestar

Yes I used only the box and the factory 7 wire.

Brian

[Jlawles2]

Great thread. I don't think it's been mentioned, but instead of using the kit mentioned in post #1, is there any reason not to use the existing 7 wire cable and just go with the junction box?

https://www.amazon.com/MICTUNING-Way.../dp/B07QDQRX7P

Also, is anyone soldering the ring terminals instead of crimping?

I did just the box and used the existing whip cord.

Solder vs crimp is the age old discussion. I will state that on one of the diesel forums there was a noted issues with soldered connections and ABS trailer systems. All of the properly crimped ones worked correctly but any soldered connections failed. My guess is the solder created extra resistance in the system resulting in signal errors with the ABS. NOW crimp then solder and you have a connection that is well prepared for everything as the crimp is the primary connection and the solder is the corrosion protection This may or may not have been done with several systems as I add and modify the camper. I did not do that in the box (probably should have) primarily b/c there is not exactly enough room to make good solder connections to the ring terminals after passing the wire through the grommet (not enough room to make the last few and pass through either doing the soldering externally). Plus to make the solder connection I typically use my micro torch since the connector absorbs so much heat. Micro torch minimizes heat into the wire after it's been crimped and cuts time to about 1/4 or less than the standard 60W iron.

[Lonestar]

I did just the box and used the existing whip cord.

Solder vs crimp is the age old discussion. I will state that on one of the diesel forums there was a noted issues with soldered connections and ABS trailer systems. All of the properly crimped ones worked correctly but any soldered connections failed. My guess is the solder created extra resistance in the system resulting in signal errors with the ABS. NOW crimp then solder and you have a connection that is well prepared for everything as the crimp is the primary connection and the solder is the corrosion protection This may or may not have been done with several systems as I add and modify the camper. I did not do that in the box (probably should have) primarily b/c there is not exactly enough room to make good solder connections to the ring terminals after passing the wire through the grommet (not enough room to make the last few and pass through either doing the soldering externally). Plus to make the solder connection I typically use my micro torch since the connector absorbs so much heat. Micro torch minimizes heat into the wire after it's been crimped and cuts time to about 1/4 or less than the standard 60W iron.

OK thanks. I'm usually a big solder fan but in this case I feel using the crimp option is certainly no issue, and I can imagine the pain of trying to solder inside the terminal box. If you ever had corrosion problems it would be easy enough to clean up with a new ring terminal, assuming there is enough extra wire. I'm looking forward to this project after the outside temps get back down in the comfortable upper nineties!