I'm having a starting issue on my 2006 F150. It's similar to what I've found in other threads, but with some other factors. Here's the story:

On Christmas day, I started taking apart the interior to prep for a stereo installation. Here's what I removed:
- rear seat back
-rear trim panels
-center dash pieces
-head unit (6-disc in-dash changer)
-climate control panel

No factory wires have been cut. This morning I went out to move the truck into the garage, and it wouldn't start. All the chimes were working, but when I turned the key, all I got was a clicking sound and the speedo and tach needles fluttering. I tested the battery with a DMM, and it was reading 12 volts.

I decided to just work in the driveway installing the new stereo gear and deal with the starting problem later. Again, no factory wires were cut. All I did today was run the RCA cables and figure out the layout for my amps, distribution block, and crossovers. I haven't installed the new head unit yet.

Tonight, I set the factory alarm using the key fob and it worked fine. I came inside to research this starting issue. After reading this thread, I went back out to check the battery again. The truck wouldn't unlock with the key fob. I turned the key, got the same result as this morning. The big difference, though, is that there were no chimes. For some reason, the headlights were on, even though the headlight switch was off. I tested the battery again, and this time it read 6.8 volts. I assume that drop is because I had the doors open all day.

Is it just coincidence that the starting issue happened just after I took apart the dash? Any ideas out there?

 

Sounds like the battery, my 05 when the battery died it would click and the headlights would come on and stay on (switch was off) did you try jumping it?

 

sounds like with the doors open and dome lights on it drained your battery or your battery has failed. you need to charge and test your battery. if its more than 3 years old or so it probably wouldn't hurt to replace it.

 

It does sound like you drained the battery. All sorts of strange electronic issues occur when these truck batteries are about to fail. Also, 12 volts is not a full charged battery. It should be more like 12.7 to 14 volts for a healthy battery. My '06 original battery just gave up the ghost last month and I replaced it. All is well again.

 

With the engine OFF, it should be around 12.6. With it running, it should be between 13.5 and 14.4 (alternator output).

 

^ more specific and correctly stated.