My son just installed a solenoid between his battery and his camper to keep his truck battery from being drained if something got left on in the camper. He asked me if my shiny new truck had that protection as part of the trailer tow package on it. We checked the socket and there was power there with the key in my pocket. This means it does not have protection or only one battery does. Can anyone tell me which it is???

 

I am not sure if it has protection or not, but I do know that one battery is not isolated from the other, they are directly tied together.

 

As Rockjeep said...The batteries ARE tied together...

IF I CAN remember correctly, the 12 to the trailer plug is CONSTANT 12V.

HTH

Tony

 

I'm not sure about the 07 but I have the tow package and I put a meter on the trailer plug in my rear bumper and there is 12 volts at all times, so looks like a battery isolator did not come with the tow package in 2004. Maybe you should do as I did and test.

On a side note, I go dry camping almost every weekend and leave my 5er plugged in and never have had a problem with dead truck battery, and have drained the trailer battery down many times.

 

Years ago I heard of one of the batteries, on diesels with tow packages, feeding through a special solenoid that kept that battery charged even if the other one got drained along with the trailer battery. My 96 did not have the tow package and I did flatten all 3 batteries on a cold nite with the furnace fan. If you flattened your trailer battery and still had juice to start your truck, I'de bet you have the protection on one battery, and it is the other one that is giving you the 12 volt reading.
Since starting this thread, I've e-mailed my dealer's tech asking him. If he answers I will let ya'll know what he says.

 

Dealer tech got back to me. Says that neither battery is isolated from trailer when key is off. Also that Mopar has no part to do that job, but should be able to find one aftermarket.