# Dodge Ram Trailer Connection Question



## MJRey (Jan 21, 2005)

Hi,

I'm getting ready to take our first trip with our new truck and tonight I was hooking up the brake controller. The instructions that came with the brake controller pigtail connector for the truck had a caution that the trucks battery is not isolated from the trailer and when the truck is shut down and connected to the trailer the trailer could discharge the battery. My previous Ford with the tow package included a trailer isolation relay to make sure the trucks battery isn't drained when the truck is off. I was a bit annoyed when I saw this note on my new Dodge since it's built for towing and has the tow package. This seems like something that should be a basic part of a tow package.

Okay here's my questions for Dodge owners:
1. Is this true or is there an isolator to prevent truck battery discharge?
2. If there is no battery isolator how to I add one or is it just easier to disconnect the trailer when stopped for extended periods?

Thanks,


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## Katrina (Dec 16, 2004)

MJRey said:


> Hi,
> 
> I'm getting ready to take our first trip with our new truck and tonight I was hooking up the brake controller. The instructions that came with the brake controller pigtail connector for the truck had a caution that the trucks battery is not isolated from the trailer and when the truck is shut down and connected to the trailer the trailer could discharge the battery. My previous Ford with the tow package included a trailer isolation relay to make sure the trucks battery isn't drained when the truck is off. I was a bit annoyed when I saw this note on my new Dodge since it's built for towing and has the tow package. This seems like something that should be a basic part of a tow package.
> 
> ...


I'd vote for unhooking the trailer during long stops.
A good battery isolater is gonna run you about a hundred bucks.
I've stopped for a couple hours at a time with my chevy and had no trouble, but I'd unhook for an overnight.


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## Y-Guy (Jan 30, 2004)

I always unhooked for over night camping, there is supposed to be one, but I never felt the need to chance it. If the trailer is able to drain the truck battery you are really up a creek, however if that truck can charge (check that you have the fuse installed) then you can always breath some life into a low trailer battery. Not like I'd now about this, not at 2:00 AM in the morning when its cold outside no no no


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## bigdisneydaddy (Oct 26, 2007)

There is a very simple and inexpensive way to isolate the battery in your truck. Since I am not familiar with the Dodge trucks I cant help with the location of the electrical items (someone else can chime in and help) You will need a 30 or 40 Amp relay commonly used for fog lights or auxiliary lighting (even Walmart has them) Find the wire from your underhood electrical center that feeds the trailer the 12v for the trailer battery. Disconnect it and put it on the #87 terminal on the relay. Connect the #86 terminal to a good ground (usually there are good ones holding the box to the inner fender, use a star washer on the ring terminal) Connect the #85 relay terminal to a circuit that is hot only when the ignition is on (use a fuse tap, wipers would be a good circuit) Connect the #30 terminal to a 12v constant source, a lot of times you can use the post that you already removed the power wire from, make sure you use a 30A inline fuse or breaker. 
you will need:

relay
a few feet of wire, black, red and whatever other color you like
4 spade terminals for the relay connections
ring terminal for ground wire
fuse tap for #85 connection
ring terminal for power #30 connection
maybe a few misc zip ties to tidy things up

On a GM truck this will all fit in the underhood electrical center and be invisible. 
The beauty is that you never have to mess with disconnecting the trailer from the truck, when you shut the truck ignition off the batteries are essentially seperate.

let me know if anything is unclear or you need anything else.

Scott


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## CamperAndy (Aug 26, 2004)

1 - It is true, the 12vdc wire is hot all the time.
2 - I do not see the need for an isolation relay. It is better to disconnect the trailer pig tail.


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## bigdisneydaddy (Oct 26, 2007)

CamperAndy said:


> 1 - It is true, the 12vdc wire is hot all the time.
> 2 - I do not see the need for an isolation relay. It is better to disconnect the trailer pig tail.


Why go to the trouble of disconnecting every time and remembering to reconnect it when you can rewire it and forget it ?

Scott


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## CamperAndy (Aug 26, 2004)

bigdisneydaddy said:


> 1 - It is true, the 12vdc wire is hot all the time.
> 2 - I do not see the need for an isolation relay. It is better to disconnect the trailer pig tail.


Why go to the trouble of disconnecting every time and remembering to reconnect it when you can rewire it and forget it ?

Scott
[/quote]

If you need to feed power to the trailer you need to turn the key on to power the relay. No need to power all the trucks internals just to feed a little power to the trailer.

This may not be an issue with some but that is why I like the always hot connection that is there. BTW I only connect the trailer plug when I am hitched and I have yet to stay hitched when camping so it seems to be a bit of a moot point for me. I have only once reconnected the trailer to the truck for power once and that was before I had a generator.


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## bigdisneydaddy (Oct 26, 2007)

CamperAndy said:


> 1 - It is true, the 12vdc wire is hot all the time.
> 2 - I do not see the need for an isolation relay. It is better to disconnect the trailer pig tail.


Why go to the trouble of disconnecting every time and remembering to reconnect it when you can rewire it and forget it ?

Scott
[/quote]

If you need to feed power to the trailer you need to turn the key on to power the relay. No need to power all the trucks internals just to feed a little power to the trailer.

This may not be an issue with some but that is why I like the always hot connection that is there. BTW I only connect the trailer plug when I am hitched and I have yet to stay hitched when camping so it seems to be a bit of a moot point for me. I have only once reconnected the trailer to the truck for power once and that was before I had a generator.
[/quote]

I understand your point now. Personally I never used the truck for power when it was turned off, I dont like the idea of the batteries equalizing and reducing the life of the trucks batteries. the reason that I did it was because we stop to sleep in the trailer while on the road. I didnt want the truck battery being drained as part of the 3 battery system (2 truck/1 trailer) and I didnt want to have the hassle of disconnecting the trailer when we stop. In the winter we are able to run the furnace and some lighting for at least 8 hrs without any problems.

Scott


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## jdpm (Apr 12, 2007)

MJRey said:


> Hi,
> 
> I'm getting ready to take our first trip with our new truck and tonight I was hooking up the brake controller. The instructions that came with the brake controller pigtail connector for the truck had a caution that the trucks battery is not isolated from the trailer and when the truck is shut down and connected to the trailer the trailer could discharge the battery. My previous Ford with the tow package included a trailer isolation relay to make sure the trucks battery isn't drained when the truck is off. I was a bit annoyed when I saw this note on my new Dodge since it's built for towing and has the tow package. This seems like something that should be a basic part of a tow package.
> 
> ...


Hey Mark.

I have a '06 RAM diesel and after about 10 minutes of the truck being shut off, it shuts down the battery to everything, including the trailer lights and brake controller. I would bet it shuts down the power to the trailer battery, too. I know so as I rectnly experienced this situation. While checking in at Disney for New Years, I pulled up to the check in booth, turned off the headlights, left on the park lamps, shut down the engine. While waiting my turn for check-in, I looked around after about 10 minutes and all my lights were off - on the trailer, the turck, and brake contoller. Perform a test - duplicate what I'm describing and see. My former Chevy Avalanche was the same way. I think the manufactures do it that way for a reason. Good luck. PCM


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## bigdisneydaddy (Oct 26, 2007)

jdpm said:


> Hi,
> 
> I'm getting ready to take our first trip with our new truck and tonight I was hooking up the brake controller. The instructions that came with the brake controller pigtail connector for the truck had a caution that the trucks battery is not isolated from the trailer and when the truck is shut down and connected to the trailer the trailer could discharge the battery. My previous Ford with the tow package included a trailer isolation relay to make sure the trucks battery isn't drained when the truck is off. I was a bit annoyed when I saw this note on my new Dodge since it's built for towing and has the tow package. This seems like something that should be a basic part of a tow package.
> 
> ...


Hey Mark.

I have a '06 RAM diesel and after about 10 minutes of the truck being shut off, it shuts down the battery to everything, including the trailer lights and brake controller. I would bet it shuts down the power to the trailer battery, too. I know so as I rectnly experienced this situation. While checking in at Disney for New Years, I pulled up to the check in booth, turned off the headlights, left on the park lamps, shut down the engine. While waiting my turn for check-in, I looked around after about 10 minutes and all my lights were off - on the trailer, the turck, and brake contoller. Perform a test - duplicate what I'm describing and see. My former Chevy Avalanche was the same way. I think the manufactures do it that way for a reason. Good luck. PCM
[/quote]

You might want to check the power at the plug and be sure. I think that the shutdown does not include that circuit since it is wired to a post on the electrical center and does not go through some of the other electronics. My only experience is with GM trucks and yours may differ.
The park lights also go off after 10 minutes on my truck, it bugs the heck out of me that I cant make them stay on.


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## jdpm (Apr 12, 2007)

Mark, I see you have signed up at DTR Dodge Diesel forum. I ee the posts there for the above question. Sounds like it keeps the battery hot. That web site is awesome, btw. LOTS of good info on there that has really helped my out. Good luck with the new truck. PCM


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## MJRey (Jan 21, 2005)

Thanks everyone for the help and information. I'll probably just disconnect the trailer for now if I'm going to be parked for awhile. One of the reasons I asked is that I sometimes leave the trailer all hooked up and ready to go overnight at my house before a trip. With my previous Fords I never had to worry about draining the truck battery. During the day it's not really an issue for me since the solar panel on the roof of the trailer will be feeding power to the trailer batteries.

jdpm, I also signed up for TurboDiesel Register and I'm eagerly anticipating my first issue. From what I've seen there's lots of great info in there. Tomorrow I get to tow the trailer home for the first time with the new truck so I'm excited to see how well it does.


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