Here's what's going on. On Saturday, I installed my Tekonsha P3 brake controller on my 2015 JKU, with factory towing package, using the eTrailer.com ETBC7 Universal Installation Kit. The new 7-way/4-way plug plugs into the existing 4-way, and a pair of wire is run through the frame, one to a 40amp relay then + battery, the other to the brake controller brake output. Another set is run from the + battery with a 30amp relay to the controller power and the - battery to controller ground. The last controller wire ties into the brake switch to activate. The install was easy, and everything worked as expected.

On Sunday I left for a business trip, no trailer, but the controller was hooked up. Again, everything went as expected. Monday morning I went to leave the hotel and the battery was dead. I unplugged the brake controller just in case that was the problem, got jumped off and drove to AutoZone to test it. They said the battery was going bad (original OEM), so I replaced it with a new, larger battery (and paid too much for it). I was late for my first appointment but got there. I want to leave after an hour or so inside and the new battery was dead. I disconnected everything from the battery that I installed with the brake controller, got jumped off and went back to AutoZone to make sure the battery wasn't defective. It checked out OK, and I haven't had any problems since, but the controller and all power have been disconnected.

When I got home I checked all my connections, checked for broken insulation, etc. Everything looks good. I took it to my mechanic friend and he did the same, and everything looks good.

The 12v at the plug always has power (when the wires are connected) but if a trailer is not connected I don't think there should be a drain. Since the 2nd time the battery went dead the controller was unplugged, I can assume it is not in that area, so it must be the 12v going back to the plug. Again, everything looks good.

When I got to the hotel Sunday night I backed into the parking space and Monday morning the sprinklers had been on and everything was soaked. My only guess is that water got into the connection (which was taped but not heat shrinked) or into the plug itself, which appears to be sealed on the back, with a flip up cap over the front. It may have been still wet after the 2nd battery was installed, which caused a ground short and battery drain. Also, if it makes a difference, both times the battery was dead I was able to unlock the doors with the remote, but everything was completely dead when I got in and tried to start it. There was no clicking which I am used to with a low battery. Immediately when I was jumped off (1st time with a battery jumper box and the 2nd with cables) it started with no hesitation when I turned the key.

Anyone run into something similar? I need to pull a trailer tonight for the football game and I have everything connected right now. I'm hoping that it was a wet connection and that it will work later today. I have a jumper box just in case. I also plan on redoing all the connections in the morning with waterproof connectors and trying to find a new waterproof 7-way plug.

 

I can't help so much with the wiring issue, but I'd add this general battery commentary. Factory batteries are generally good for about 2 years +/-, so yours going out was right on schedule if not a little late. When mine went out abruptly at 2 year (like clockwork), I didn't have much time to research as I was out around town. I got a Duralast Gold from Autozone. I just returned from Moab this weekend, and speak of the devil.....pulled in to my driveway to unload the jeep and get the top off. Went to pull Jeep in the garage and battery dead! Pulled it out and headed to Autozone.....I had 10 days left on the battery's 3-year warranty! Fancey that! New battery at no cost. Not sure what you bought at Autozone, but you might just make a mental note 2.5 years out to start watching that battery again.

 

did you connect to the correct brake switch wire? more than one person has made that mistake. it is a stupid small wire and you need to be a contortionist to get to it.

 

I bought the Duralast Platinum, which was the lowest model they had in stock. They had an Optima, but it was an extra $50 and had lower cranking amps.

I can understand the first problem, but not the new battery draining so fast. I'm headed out to the parking lot in a few to see if its dead now. Thanks again.

 

I believe I did. Everything works like it should, and the brake activates when the pedal is pressed. And yes, the wire was hard to get to and I still have a bruise on my ribcage from laying on the door sill.