Battery Isolator

[Picinisco]

Does the tow package included on the 2005 3500 dually include a live centre terminal on the 7 way bargman socket to charge the trailer battery while the engine running.

 

[crash68]

Yes there is a 12+ that stays hot all the time in the seven pin connector. If I remember correctly, it's fused at 30 amps. The center pin is reverse. Looking at the connector, it's the one on the upper right.
Attached is how 7 pin connectors are wired (both trailer and truck side)

 

[Picinisco]

Got it. So #4 is constantly hot and will charge the trailer batteries but I would like to change that to hot ONLY when the engine is running, i.e. directly from the alternator. Is this a thing.

 

[crash68]

You would have to figure out how to wire a relay in line with the existing wiring and/or fuse. Or just unplug the trailer when you park the truck. If you have the factory brake controller (ITBM), it will let you know if the trailer is connected (or check by using the manual slider).

 

[Picinisco]

You would have to figure out how to wire a relay in line with the existing wiring and/or fuse. Or just unplug the trailer when you park the truck. If you have the factory brake controller (ITBM), it will let you know if the trailer is connected (or check by using the manual slider).

Yes that'll work.

 

[kad]

You could use a dedicated isolator like this one:

https://www.etrailer.com/p-TR118665.html

-K

 

[Picinisco]

You could use a dedicated isolator like this one:

https://www.etrailer.com/p-TR118665.html

-K

That is where I started questioning what I may already have. Seems like the constant +12v black wire does the same however I am thinking I do not want full time but rather only powered with the engine running. So would like to have the black wire connected to the alternator.

 

[kad]

That is where I started questioning what I may already have. Seems like the constant +12v black wire does the same however I am thinking I do not want full time but rather only powered with the engine running. So would like to have the black wire connected to the alternator.

Not quite. The 12v constant from the trailer plug is always on. Adding the isolator into the system would cause that wire to turn off when the engine is not running, which is what I think you're looking for.

-K

 

[sandawilliams]

Not quite. The 12v constant from the trailer plug is always on. Adding the isolator into the system would cause that wire to turn off when the engine is not running, which is what I think you're looking for.

-K

That's what they used to use on Fords and other vehicles for the starter solenoid. You would need an ignition wire for control that would become hot when the ignition was turned on and then the trailer hot lead feed up and through the solenoid. On the 2500's fuse box there is an 'upfitter' hot source fuse that will work as a good power source for the control as it is only hot when the ignition is on. Then find the correct wire feeding the plug at the back of the truck. I used this on many overhead campers over the years and it works great.

 

[Picinisco]

Do we know where the black +12v wire originates.

 

[kad]

Do we know where the black +12v wire originates.

In the TIPM (ak fuse box) under the hood. If I were going to install an isolator I would do it back at the trailer plug though. The wiring is easy to access there.

-K