Ram 1500 trailer tow 12v charge wire

[copcarguy]

Hey all!

Just a question about the 7 way trailer connector on my truck:

I noticed today that the 12v charge circuit on my '17 Ram 1500 has constant power and isn't "keyed" with the ignition. On my old '07 F-150 when you shut the truck off this line would also shut off.

We tow a travel trailer and I'd hate for it to drain the truck battery if we stopped for the night at a rest area for example.

Is there a way to change it from constant to ignition powered on my new Ram?

I know I could unplug the camper everytime we stop, but that's a PITA.

Thanks!

 

[AVB]

What is it charging? A break away battery? I wonder if it goes off when the system goes to sleep.

 

[irv]

Originally Posted By: copcarguy
Hey all!

Just a question about the 7 way trailer connector on my truck:

I noticed today that the 12v charge circuit on my '17 Ram 1500 has constant power and isn't "keyed" with the ignition. On my old '07 F-150 when you shut the truck off this line would also shut off.

We tow a travel trailer and I'd hate for it to drain the truck battery if we stopped for the night at a rest area for example.

Is there a way to change it from constant to ignition powered on my new Ram?

I know I could unplug the camper everytime we stop, but that's a PITA.

Thanks!


That's a strange one? Although I have never used the large RV plug, I have used the smaller/regular plug many times hauling my snowmobile trailer and boat and have never experienced this.

I'd something isn't correct and should be looked into but maybe check other Ram or RV forums first before you start tearing into things.

Good luck.

 

[eljefino]

That's weird. If there aren't diodes then the trailer battery is boosting your truck's battery every time you start the truck. This power surge could blow fuses. You absolutely can re-wire this, but it would take a long run of wire if you don't have schematics to work with. I'd use something from the "IGN 2" (not necessarily its name) that "mutes" when you turn the key to start. The fan blower motor uses this switch position along with stuff like heated seats.

BTW how big is the trailer battery? I found a 12 Ah one on a trailer at work-- your typical main battery is at least 80 and probably even more with the tow package. The little one should reach/maintain equilibrium with the main one and not drain it unless it has serious issues.

 

[Audios]

It may just be supplying power until the CAN bus shuts it down.Leave a test light hooked up after you lock it and see if it shuts if out when it goes to sleep.

 

[copcarguy]

Thanks for the replies so far!

The camper battery is a group 27 deep-cycle RV/marine battery.

I picked up a 7 way tester: https://www.curtmfg.com/part/58270

I'm going to try to see when I lock the truck if maybe the power shuts off after 30 minutes or something like that like AVB and Audios said above.

 

[DuckRyder]

A bit of googling seems to indicate that it is in fact 12V all the time. Some replies on other forums indicate that it may have its own fuse. If that is the case you could pull the fuse or perhaps even wire in a relay if you are concerned...

 

[beanoil]

I wouldn't be concerned about 12 hot all the time in the 7way, with the caveat that RV manufacturers are notorious for using cheap 12 volts charging systems that keep the RV battery in less than optimum condition. Primarily low voltage, and a tendency to sulfate the plates. This is why RV batteries don't last as long in the application as they do in boating deep cycle use.
Quickest way to isolate the battery is not at the vehicle, it's in the RV battery box with a quarter turn disconnect switch.

Smart RV Charging
Convert to series 6v.

 

[64bawagon]

As was mentioned earlier, your truck may have a voltage protection feature that will shut the circuit down when the battery starts to drain. If you cant confirm that its pretty simple to isolate the circuit. You would need to find the line that feeds the circuit (typically in the underhood electrical center) Cut that wire and connect the wire from the power to the #30 blade of a standard automotive relay, then place the end going to the trailer plug on the #87 blade of the relay. Run a wire from the #96 blade to a good ground and then find an ignition only circuit in the panel and tap into that using a piggyback style fuse tap, connect that to the #85 blade (amp rating can be anything since this circuit only pulls a minute amount of power for triggering the relay)
This will change the circuit to an ignition on only and will disconnect it when parked.

 

[neil57]

The 12v power terminal is to maintain your trailer battery as you drive, if you don’t want that feature pull the fuse that supplies it. My truck came without the fuse installed and directions on what it was for and where to install in fuse block. Never have had an issue with it draining truck battery overnight, I unplug when at a campsite.

 

[JTK]

Like said, this lead is typically power all the time on the 7-pin round connector. Ignition on or not.

Funny you should mention the 12VDC constant wire. I had a huge run-around recently with my FILs 2017 Nissan Frontier pickup. The wire for the 12V constant (black) and the wire for the electric brake (blue) were reversed from the factory! On Nissans, these two wires terminate at a two prong plug at the back of the vehicle. The RV place that installed the hitch and brake controller couldn't figure it out, nor would the dealer touch it because of the aftermarket parts. even though everything was plug-n-play. I eventually figured it out myself by emailing Tekonsha, the manufacturer of the brake controller. They sent me a *.pdf on the issue.

 

[mx5miata]

Charge the trailers battery

 

[copcarguy]

As an update, I plugged the tester in and forgot about it for 2 hours. When I came back it was still illuminated:



So unplug the camper on extended stops for now...

 

[meep]

Odd. Every factory tow connector I've known fed that terminal through a relay. In my 2008 grand chero one had to reprogram the BCM to fire that relay to get power back there, or else it was a dead circuit, so the daimler/dodge family at some point had it switched. I wonder when they changed. You could trace the harness and insert a relay inline with the coil triggered off an acc circuit somewhere. OTOH, leaving it in play also provides the benefit of an overnight charge to the truck if connected with the converter powered up, provided that the additional load on the converter charge doesn't pop the 12VDC fuse. I'd probably just pull the plug at night when stopping.

You might be able to insert a relay inline merely by tapping into it with the fuse terminals.

OTOH, have full time power back there can be useful for running utility lamp, air compressor, etc if you build a 7 prong plug to go into it. I run a power drill off my 7-pin to raise and lower the jacks. it was a 14v model with a dead battery, so I gutted a battery and ran 12V wire into it. works great, every time.