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Old 03-28-2011, 10:56 PM   #1
Join Date: Sep 2006
Posts: 74
Tow Vehicle battery drain

Recently the "check engine" light on my 2010 Dodge Ram diesel came on while towing my FW. I didn't think much of it until I left the trailer electrical cable connected for a few days after a trip and found the truck batteries totally run down. I now know I should not do this but my Dodge dealer checked the "computer" and it said the battery voltage was low and that was what originally turned on the diagnostic light. Since this was before the battery drain problem was experienced I am wondering if there is a problem in the trailer electrical system that was pulling down the truck battery voltage. I have a 2010 Sabre FW. I have a disconnect on my trailer battery that leaves only the battery monitor on (less than 100 mA) when open and this was open when the couple of days sitting drained my truck batteries. Any thoughts?

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Old 03-28-2011, 11:35 PM   #2
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Never looked at the Dodge wiring for a trailer connector. Ford, I know, and Chevy, I think, have a relay, that only connects the truck and the tow vehicle while truck switch is in the "on" position. If Dodge has a relay, yours may be bad, as in shorted and always connected. You also might want to make sure you have everything turned off in the camper, lights, antenna booster, water pump, etc.

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Old 03-29-2011, 05:57 AM   #3
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On my 2004 Dodge Ram 1500 - the 7 wire plug is always hot for trailer accessories
- you can check your's with a meter to verify since your's is a 2010 - they may have made some changes that I am unaware of since you are on the canbus and I am not.

Could be that the charger is going bad - it is electrical and anything is possible

Or you got a bad batch of Junky chrysler batteries even though I had my original battery up to about a month ago - I have heard of people getting bad batteries from the factory - unless things have changed
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Old 03-29-2011, 11:07 AM   #4
Join Date: Sep 2006
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More things to check

Thanks all. I had the truck with the dealer and they said the batteries were "fine." I need to see how and when things are connected to the trailer. I have a battery disconnect switch for the trailer but I am assuming all trailer stuff is still connected to the power from the tow vehicle even if the trailer battery is not. That would explain the drain if power remains in the connection. Now, where is my volt meter?
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