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mfoster711's avatar
mfoster711
Explorer II
Sep 13, 2015

Really dead battery??

I went to pickup my camper today and the electric trailer jack was not working. I assumed I had a dead battery so I hooked up the umbilical cord to the tow vehicle and tried again with the engine running. Nothing. I flipped all the breakers, checked fuses and everything looked fine but I was not getting any power any where. I wasn't even getting a dim light from any of the lights.

I thought I had an electrical problem so I got the manual crank out and hooked up the camper. Before I left the storage lot I checked the lights again and to my surprise, they were now working.

So here is my question, I thought once you hooked up the camper to the tow vehicle with the umbilical cord, as long as the engine was running, then at least the lights would work. But, I was getting nothing at first. I thought the lights would work even without a battery in this situation??

Not sure if it is relevant, but I did not have the trailer connected to the hitch when the lights were not working at first. Don't some trailers needs the hitch hooked up to establish a ground connect?? I only recall this on smaller flatbed trailers that only have the 3 wire connection and did not think it applied in my situation.

So why was nothing working at first? Was the batter just so dead it needed 5 minutes to get a minimal charge? Or do I possibly have an electrical problem that will show up again?
  • What is the measured voltage of your depleted battery? It's quite possible that the battery was completely discharged to the point that the small charge current from the vehicle could not power any 12 V devices. BTW, discharge one of those cheap Marine hybrid batteries like that a few more times and your battery will be DOA.
  • IF the 7 pin is wired correctly. You do not need to be on the ball to power the TT. If not. then the ground was made when you hooked. You should for sure get that checked, as eventually the lights will begin to flash on, and off as you drive.

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