Hello,

I have a 2007 V6 Mustang that just started having this issue. I am the original owner of the car and there have been no aftermarket mods done to it.

Sitting in the driveway, while not running, the cars headlights and taillights will randomly turn on for 30 seconds or so and then turn off. At first I thought maybe my key-less entry was being pressed by something, but this is not the case and the door remains locked when this happens. Anyway, this happened enough through the night that the next morning my battery was dead.

Anyone else had this issue or know of a cause?

 

Water getting in the smart junction box? (I think that's what it is called)

 

Agree. See if there are any signs of water in the passenger floorboard or up under the dash, behind the glove box.

 

SJB is gettin' wet. And/or is fried, which would be the unfortunate end result.

 

+1, most often indicator of plugged cowl drains.

if passenger floor carpet is wet, unhook battery, pop the passenger kick panel cover off, its likely wet in there- unplug/remove/dry the SJB(and connector plugs!), if youre lucky it might be ok- mine was, and its been wet twice- once when window/door molding seals failed, once when cowl drains plugged up- moved harness around since, and cowl drains shouldnt cause it again.

the floor/carpet is a problem, it wont ever dry without help- I dried mine by popping the door threshold off(its just taped/clipped in place- lift outside till tape pops loose, push in/up, the clips pop out of the floor) then pull the entire kick panel bottom towards inside and back towards door opening- it also pops right off, then lift/fold carpet back... I tore the padding off(its kinda glued to carpet) hung it up to dry, wiped up the floorpan, propped carpet up, let a dehumidifier run blowing that way overnight. found it needed 2 days+ even with the carpet up/fan blowing... if the carpet isnt lifted, it will stay damp underneath

i stopped the cowl drain from repeating the problem by raising the harness across the toeboard, and taping it higher- ugly, but under carpet where no one will ever see it... leaves a driploop towards the transmission tunnel, as i could see where rain water had ran down the harness to the sjb plug. I also removed the sjb bolts, forget exactly how, but put plastic sheet behind the top, bolted back down, flapped it over the front plugs, like a umbrella, so if the window molding started leaking again, it couldnt run down the a-pillar onto the top of sjb.

last time wet floor happened, took the wipers/cowl covers off, cleaned and 'goop' adhesive was used to glue/seal the 10 plastic inserts into the cowl at base of windshield.
pretty sure the three water sources are now at bay, but who knows...its as if ford designed these cowls to leak. ten years and the bad designs are showing

theres numerous threads on leak fixes, i'll look for pics of the sjb/harness changes that can help keep it dry

 

Like most have said probably a wet SJB. You say no mods, but have you done anything that requires tapping into the electrical system? If you tap into the 5V system by mistake it will cause weird electrical problems.

 

Thank you for all the responses.
So I checked the SJB and it is bone dry as well as everything around it.
Also, no, I have not done anything to the electrical system either.

I did see on another forum someone had mentioned that a bad side indicator light gave them the a similar issue once. That didn't make any sense to me, but I looked anyway. Sure enough my driver side one was out. Changed it and the issue seems to have stopped, but time will tell. If that actually is the cause, I have to imagine that there is another underlying issue somewhere.

 

That's super good news. Thanks so much for sharing.

 

That is absolutely bat **** crazy. Having said that, I'm not surprised. The electrical systems on these cars are crazy. I'm glad you found a potential fix. Thanks for updating us.

 

It is amazing how an odd condition in one area can affect something totally unrelated. My wife's '05 Saturn had an issue where the factory alarm would go off for no reason on rare occasion. Then the gauges started acting weird. It was like they were sampling their signals at a much slower rate. The speedometer and tach were jumping up or down in large increments.

A little internet sleuthing led me to clean the door jamb switch on the passenger door. That solved all of the problems. I guess with cars now essentially being a large network of sensors on a databus, an out of tolerance signal can corrupt data everywhere.

 

thanks for the tip- thats a new one to watch for

crazy how intertwined stuff can be on some cars. my old Mark Vii if the battery got a little low from sitting too long, the speedometer- even more weird, also the odometer- would sweep with the tach until fully charged back up...really weird seeing the miles tick off while parked in your driveway

 

Ok, puttin' that in the toolbox for later. Much obliged for the update, and thanks for the information!

/weird. Really.

 

Wow... OK, one to file away for future reference!