Wiring harness charge/drain battery

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geoco1953

Member
Joined
Aug 2, 2007
Posts
16
Greetings,

I am having several learning opportunities from recently having to replace the converter in my fifth wheel.

I am now doing a little more analysis of my entire electrical system.

I have a 2005 Dodge Ram with a seven pin wiring harness.  This includes a pin for charging the trailer battery.

This pin is "hot" even without the ignition on.

My question is Does the Dodge have anything in it to prevent the trailer battery from draining the truck battery while boondocking.  I have heard of an isolator being necessary.  My understanding is this is in the truck wiring, not the trailer.  Is this correct?

If it is in the truck (or I guess wherever it is), how do I go about testing to see if I have one and it is functioning?

The Dodge dealer was no help in that he says the trailer converter takes care of that.  Well I know that's wrong.  Perhaps he was thinking of the trailer power distribution center.  But, I thought this problem needed to be taken care of via the tow vehicle's wiring.
 
If it's hot with the ignition off, then it probably doesn't have an isolator as that would make it hot only when the engine was running as it would be getting power from the alternator.  It may have a diode but I wouldn't count on that.  You could put a relay in series with the hot charging lead that would be energized with the ignition or just unplug the trailer when parked.
 
I wonder if the "trailer battery charge" is looped into the Dodge's "load shedding" program which will turn the lights off after a few minutes if the ignition is not on.

The power outlets (cigarette lighters) are NOT in this program and I imagine the hazard flashers wouldn't be either (although since they turn on and off, this may not be perceived as a constant drain).

Does anyone have any ideas how I might test this circuit or how I could get an answer out of Dodge?
 
The attached photo shows the pin wiring for my 2005 Dodge Ram 1500.  My pickup hadn't been started for 12 hours and checking the + pin with a volt/ohm meter, the pin was not powered.


Edit:  I also check it with the key on and with the engine running.  The + pin was not powered on my pickup.
 

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Lowell,

It would seem then that you are not charging your camper battery from the truck.  If you want to charge it, first check the fuse.

At fisrt, I had NO power on mine either.  Via the Dodge dealer, I learned that the factory installed hitch wiring is fused through the fuse box located in the engine compartment. 

There is a handy diagram on the back of the fuse box cover that lists all the fuses.  Turns out there is a separate fuse for just about each pin on the hitch receptacle.  My fuse for the "trailer battery circuit" was blown.  It has been replaced and all appears to be working at the receptacle.
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Thanks geoco. It has not been a problem for me but I will check the fuse box. I might as well charge the TT battery while driving if I can.
 
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