Problem with Backup Light on Tow Vehicle

[Uncle Chan]

All,

I have a 2006 Dodge Charger with a factory RV plug (7 round). I also have a Mobi TD. I usually tow with a F150 and have never had a problem. We've decided to start towing with the Charger. The problem is that when I plug in the TD, the Charger's backup lights come on. When I disconnect the charge wire to the TD's battery, the backup lights don't come on. So, there seems to be a problem with the charge wire.

IF the Charger's wiring is not setup to charge the TD, is it possible that the backup light would come on when a hot wire from the TD's battery is being fed back into the Charger?

I'm a real novice here, so any help would be very much appreciated. I don't mind not having the battery charged when being towed, but I want to make sure that I'm not harming the Charger.

***UPDATE***

After doing some research, I've learned that the Charger's center pole of the 7 RV plug is for the backup lights. The center pole for the TD's RV 7 is for charging the battery. Seems that I'm backfeeding into the Charger and lighting up the backup lights.

So, by disconnecting the TD's charge wire, I will eliminate the back feed. That should resolve the backup lights issue, but not the battery not charging issue. Oh well. Baby steps.

Thanks,
Uncle Chan

[teardrop_focus]

Glad you discovered the issue. You might be able to make and adapter? if you still own both tow vehicles...

Order another 7 round connector (both tug and trailer) and wire them in a fashion that will alter the trailer wiring to the Charger's schematic... that might work. I think I know what I mean.



You'd have two more connector pieces in the electric hookup while towing w/ the Charger, though...

[bobhenry]

I would be checking the wireing on both and try and standardize them. Here is the most commonly accepted codeing.





since the backup lights would be most commonly on the auxilary post I would suspect the trailer because there is 12 volts being back fed to the back up lights indicating the car is correct and the auxilary is feeding from another source back to the tow vehicle. With the trailer disconnected energize the auxilary on the trailer with a battery or battery charger and start checking to see where all the juice goes.

[Uncle Chan]

Well, you are both right. The diagram on the Charger plug shows the center post used for backup lamps. Whereas the standard plug configuration (the one on the TD) shows it to be used as an auxillary (AKA, charging).

So, I'll go without charging and just disconnect the wire from the battery. No worries. I always plug in a charger if/when I can anyway.

[Dale M.]

Your concepts are correct (trouble shooting) but the problem is in car wiring and not trailer, your solutions/fixes need to be on car side of connection....

Why not disconnect backup light wire from plug (aux pin) on "Charger" and wire a 12 volt "charge" supply (from car battery) to aux pin (on "Charger") for battery charging..... That way all vehicles would be consistent, and no adapters involved....


Dale

[Uncle Chan]

Your concepts are correct (trouble shooting) but the problem is in car wiring and not trailer, your solutions/fixes need to be on car side of connection....

Why not disconnect backup light wire from plug (aux pin) on "Charger" and wire a 12 volt "charge" supply (from car battery) to aux pin (on "Charger") for battery charging..... That way all vehicles would be consistent, and no adapters involved....


Dale

Dale, I would like to do this, but lack the comfort level and expertise to do so. The Charger's is hardwired into the system. I would be afraid that I would mess something up.

[dh]

Your concepts are correct (trouble shooting) but the problem is in car wiring and not trailer, your solutions/fixes need to be on car side of connection....

Why not disconnect backup light wire from plug (aux pin) on "Charger" and wire a 12 volt "charge" supply (from car battery) to aux pin (on "Charger") for battery charging..... That way all vehicles would be consistent, and no adapters involved....


Dale

Dale, I would like to do this, but lack the comfort level and expertise to do so. The Charger's is hardwired into the system. I would be afraid that I would mess something up.

Easier option:

Trace wires coming out of 7 pin on the Charger, so lets say the center pin is the back up light, and it happens to be, lets say, orange. Snip the orange wire a few inches from the plug, and your back up light problem is solved. Now, lets just say you had an "oh crap" moment and cut the wrong wire, no problem, you left enough room to repair, just crimp the wire back together and put some heat shrink (or whatever your favorite method for insulating wires) over the crimp, and move on.

Also, does the Charger have a "hot" pin on its 7pin connecter? if so, snip it a few inches back from the connecter and crimp it onto the tail comming out of the 7 pin for the center plug.

DONE!!!

You also left enough room for error. Remember, you are just moving wire to different pins on a connecter, not rewiring the entire vehicle, the worst that you can do is cut power to a wrong pin, which you will find out with your meter, and can fix. Absolute worst case senerio, you blow a fuse, or have the wrong light come on at the wrong time.

[Corwin C]

I'm charging the trailer battery using pins 1 and 4 (black and white) on bobhenry's diagram above (factory wiring on '03 Chev Tahoe.) I'm also using the center pin for backup lights.

I was wondering ... is there another reason to have 12v. directly to the trailer other than to charge the battery? Unless, of course, the trailer doesn't have a battery and you are using the TV battery to run items in the trailer.

As far as cutting wires ... I would just disconnect them at the plug (most plugs are 2 screws to open the housing and 1 screw for each connect/disconnect.) I would also apply some electrical tape to the end of the wire to avoid a short if it is not connected. This provides for "unlimited" tinkering.

[Tumbleweed_Tex]

If, after trying all of the above with no success, simply remove the wire from the center terminal on the trailer end, and attach it to the #4 terminal instead. Backup light problem solved, and the TD battery will now charge properly as well...no matter which vehicle you tow with.

[Dale M.]

If, after trying all of the above with no success, simply remove the wire from the center terminal on the trailer end, and attach it to the #4 terminal instead. Backup light problem solved, and the TD battery will now charge properly as well...no matter which vehicle you tow with.

Actually this is probable the correct thing to do..... I was close but not quite correct...

It just means verifying "connectors" in both tow vehicles and changing if necessary.... As for comfort level its about a .5 on scale of 1 to 10...

You should only be dealing with pin 7 and pin 4.... And usually connector are clearly marked by color or pin numbers...

Dale

[dh]

As far as cutting wires ... I would just disconnect them at the plug (most plugs are 2 screws to open the housing and 1 screw for each connect/disconnect.)

Not true of factory 7 pin connectors. They terminate in a plug, and this plug goes into the 7 pin. Its all robotically crimped and put together.

A replacement, or after market plug, yes, just swap wires on pins as you described, but a factory job is not doable.

[Uncle Chan]

As far as cutting wires ... I would just disconnect them at the plug (most plugs are 2 screws to open the housing and 1 screw for each connect/disconnect.)

Not true of factory 7 pin connectors. They terminate in a plug, and this plug goes into the 7 pin. Its all robotically crimped and put together.

A replacement, or after market plug, yes, just swap wires on pins as you described, but a factory job is not doable.

Correct. I cannot just swap, cut, or replace. My unit is factory installed and sealed.

I will have to make do. It is what I do.

[PanelDeland]

Put a heavy duty toggle switch in the charge line for the trailer.When you tow with the Charger just flip the switch to off.You'll know if it's on since the back up lights will be on.The downside is that the trialer will not charge is you forget to turn it back on.

[Uncle Chan]

Put a heavy duty toggle switch in the charge line for the trailer.When you tow with the Charger just flip the switch to off.You'll know if it's on since the back up lights will be on.The downside is that the trialer will not charge is you forget to turn it back on.

Great idea! Thanks!

[Tumbleweed_Tex]

Just so I understand correctly…

Are we saying that the 7 pin connector plug on the Mobi is factory sealed, and it is impossible to get inside that plug to move one wire?