Trailer charge line draining trailer battery while engine off

kleake

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Anyone ever leave your trailer plugged into the truck while it's not running and have it drain your trailer battery? Once the truck starts it's charging fine, but shut it off and there is about a 1amp drain on that line. Pulled the relay and unplugged the trailer, test light on positive, probe on the relay terminal to the trailer plug and it lights my test light dim. I've heard of water being in the trailer plug and I think I sealed that up a few years ago. Not sure if it's in the plug or somewhere in the wiring. I only have the factory plug at the bumper, nothing added in the bed or anywhere else.
 

ithumpwheniwalk

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I've towed 5th wheels and bumper pulls for years and never leave em plugged in once the truck is parked. At least not for more than a few hours, but it has always been my experience it will kill your battery if left over the weekend etc...
 

kleake

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I've towed 5th wheels and bumper pulls for years and never leave em plugged in once the truck is parked. At least not for more than a few hours, but it has always been my experience it will kill your battery if left over the weekend etc...

It's not killing the battery on the truck, which is normally what it will kill due to the trailer drain. The truck has a relay to shut off the charge line to the trailer when you turn the key off, what is happening is the truck is then killing the trailer battery while sitting due to some draw on that charge line on the truck side. My utility trailer can sit for weeks by itself and the battery is fine, but plug it into the truck overnight and it's at 0V. The truck starts right up and starts charging the trailer again. Some sort of parasitic draw in the truck wiring.
 

lincolnlocker

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It's not killing the battery on the truck, which is normally what it will kill due to the trailer drain. The truck has a relay to shut off the charge line to the trailer when you turn the key off, what is happening is the truck is then killing the trailer battery while sitting due to some draw on that charge line on the truck side. My utility trailer can sit for weeks by itself and the battery is fine, but plug it into the truck overnight and it's at 0V. The truck starts right up and starts charging the trailer again. Some sort of parasitic draw in the truck wiring.
If there is any moisture in any of the plugs that lead to the trailer it may have a cross connection through the moisture if its enough. Id take apart the pig tails from the main wire harness in the rear of the truck to the trailer and make sure they are clean and dry. I know you dont deal with salt or sodium chloride like we do i the north but that chit in liquid form can wreak havoc on electrical connections and components.

live life full throttle
 

kleake

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Haha, well, my own fault.... I finally had a chance to trace it down and forgot that I power my backup camera from that line since there wasn't any other wires back there to run it from. I like it powered all of the time the truck is running so I can view it while going down the road in case a safety chain comes loose. So, when the truck is off, the trailer backfeeds and powers up that camera. Minor draw, but was enough to drain those little batteries in the trailer.
 

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