This afternoon, I tried to start my truck after a couple of days of inactivity and it wouldn't start until I jumped it off. I then drove around for an hour or so and shut down, putting a battery tender on it.
Tonight I step into the garage and I hear some rapid clicking from underneath the hood. When I try to open the door so I can unlock the hood, it won't unlock using the power button. The courtesy light wouldn't come on either. Obviously the battery has run down again. I use the key to unlock the door, then pop the hood.
I track the clicking noise down to a relay which I believe is 46B (fog light relay). I pull the relay out and then put a regular charger on the battery.
I bought this 2007 truck in 2010 with 68k on it. The battery in there is a Motorcraft which I believe is probably the original battery. Externally it appears to be in excellent condition and the posts/connections are all clean. I recognize it's probably reached the end of its useful life.
I noticed some weird things: 1) with the truck on the charger and the fog lamp relay removed, the charger is drawing about 7-8 amps (after an hour or two). The door locks engage when I open the door. I then hit the door lock button and they disengage. I shut the door and they stay disengaged. I try to open the door again and the locks relock themselves. 2) I plugged the fog lamp relay back in and the fog lights come on. This is independent of the fog lamp switch position, which is off. The charger draw goes up quite a bit. The only way to turn the lamps off is to pull the relay. The charger draw drops back down to 7-8 amps.
Now I suppose it's possible the fog lamp relay got stuck on and that's what ran my battery down. But I didn't use the fog lights! The switch was off when I checked it.
I am OK with buying a battery as I'm sure I got my money's worth out of this one. But what else is going on? Should I just replace the fog lamp relay relay and see what happens? (While it initially was clicking rapidly when I first became aware of all of this, it no longer makes any noise when I plug it in; the fog lamps just turn on.)
What I am really trying to avoid is multiple trips to Autozone. I live on a barrier island and the closest auto parts place is 11 miles away on the mainland.