Battery Drain When disconnecting RV

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Folson

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Hello New to the Forum. I have I believe a unique situation and was hoping that someone may have had the same. For the last 2 years I have noticed that when I disconnect my RV from the truck and it sits for a couple of days the battery will drain not starting the truck. 2 different RV's, new 7 pin and brake controller. Also dealer could not duplicate with out RV. Obviously a drain after the RV is disconnected. The crazy thing is after using (with RV disconnected) when jumped etc the truck after disconnected I can leave the truck parked for days etc and it will start? Obviously again something is staying on after the RV is disconnected then shuts off eventually. I found a discussion where supposedly their is 4 relays under the Power Distribution center for the tow circuit but it is a little confusing as it seems that may not be plug in's . Of course on the PDC there are fuses for the tow circuit. The schmatic also showed the Module Body Control in the circuit? I assume this is the connector? Anyway with not being able to find the drain will a battery disconnect work? And if so what should I use? Thank you
 

crash68

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I found a discussion where supposedly their is 4 relays under the Power Distribution center for the tow circuit but it is a little confusing as it seems that may not be plug in's . Of course on the PDC there are fuses for the tow circuit. The schmatic also showed the Module Body Control in the circuit?
The four relays in question are what power up the Left/Stop, Right/Stop, Reverse and Running light circuits to the trailer plug. Those relays are built into the APD (fuse box) and get the signal to turn on via the BCM. There is 12V going to the relay and it grounded by the BCM. The relays send power through the fuses before heading to the back of the truck. It would be easy enough to troubleshoot if any were staying on using a test light on those pins at the 7 pin plug after unplugging the trailer.
 
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Folson

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Thank you. Yes I agree. I did see power on 2 of the pins the + pin and Brake Control pin. When I disconnect the brake controller that pin goes to zero. but still have power at the + pin. But the voltage I am reading is 0.10 on both pins where the others are basically 0. 0.01 The brake controller and 7 pin have been replaced. This is all without the RV being plugged in and out. My thought is that the next time we use the RV I will test at the fuses with the battery neg off and a meter to see if the fuses have any power and at the 7 pin as you suggested. But this all being said without changing the relays which appears cannot be done the APD would need to be replaced? So would a battery disconnect work? and if so on the neg or pos side? Thanks again for all your help
 

SitKneelBend

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Thank you. Yes I agree. I did see power on 2 of the pins the + pin and Brake Control pin. When I disconnect the brake controller that pin goes to zero. but still have power at the + pin. But the voltage I am reading is 0.10 on both pins where the others are basically 0. 0.01 The brake controller and 7 pin have been replaced. This is all without the RV being plugged in and out. My thought is that the next time we use the RV I will test at the fuses with the battery neg off and a meter to see if the fuses have any power and at the 7 pin as you suggested. But this all being said without changing the relays which appears cannot be done the APD would need to be replaced? So would a battery disconnect work? and if so on the neg or pos side? Thanks again for all your help
Given the symptoms, I'm betting a negative battery cable disconnect will do it as a work around.
 
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Folson

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SitKneebend; Well thats what I believe too. So on the Negative side. Do you have any experience on which one would work best? Thanks
 

SitKneelBend

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SitKneebend; Well thats what I believe too. So on the Negative side. Do you have any experience on which one would work best? Thanks
I'm not sure the context of your question for "which one would work best"?
 
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Folson

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Thanks Sorry for the confusion. Basically looking for a recommendation of which product. I know of the post ones and watched some You Tube's video's. But with this symptom just wondering what maybe the best option. I read some discussions that the Knife switch one can be unsafe.
 

SitKneelBend

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Thanks Sorry for the confusion. Basically looking for a recommendation of which product. I know of the post ones and watched some You Tube's video's. But with this symptom just wondering what maybe the best option. I read some discussions that the Knife switch one can be unsafe.
Ah, that I'm unsure of. I haven't used any kind of disconnect. One thing to note, after disconnecting the battery the factory radio will take several power cycles to display everything properly.
 

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Are you sure the battery on your RV is good? When plugging in the RV you essentially put 2 batteries in parralel and it could simply be that the alternator cannot keep up with charging both thus limiting the charge to your truck. It is also recomended that the RV is plugged in to street power at home to prevent the battery drain.
 
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Folson

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chopperman1 Thank you. This symptom is 2 differant RV's. One of the things I never did was measure the battery once we have disconnected. The Rv we do not leave connected. But based on everything being said and help I'll try the measurement when we use the RV next but also think a disconnect will be a solution also and testing the circuit the next rv trip. My concern is if I use a disconnect will it hurt the truck having the battery disconnected for awhile? Another idea I had was to put a trickle charger on the battery when we disconnect also.
 

chopperman1

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A disconnect will cause your truck to continually go in to relearn mode on essentially all of your adaptive systems. This is not a good idea on my opinion.

Have you tried simply plugging in your RV at home, starting up truck, apply brakes, turn on directionals, shutting it off, then unplug it, let it sit overnight and see if it duplicates? That will tell you if it's from the towing/camping time or RV drawing too much vs something in the truck.
 
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Folson

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Hello Yes that is a good plan and I agree about the Disconnect but if I cannot fix or find the issue? Unfortunately I have to go to the storage to do all the testing etc as we have downsized and we no longer keep the RV at the house. But that is the plan now. By the way your profile pic is cool. I'am retired military 19D/19E
 
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