Really Weird Electrical Problems - Ideas?

I'm so confused and scared right now...I can't figure out for the life of me what's going on with my car. It started with me trying to start it after the car had sat for a week or so while I was working on engine mounts, and only the fans turning on. I checked the fuses and none were blown, so I checked the switched wire at the starter, and it was giving me no voltage. I then unplugged the battery and went inside to take a break. When I came back out and plugged the battery back in, I noticed that the trunk light didn't turn on. I looked at the dash and the door open light wasn't on either. I tried turning on the parking lights and they didn't turn on. I tried the horn and it didn't work. Basically, nothing on the car works. This is where it gets confusing. I've got a fuse 6" from the battery, and it's in good shape. Figuring I'd popped some other fuse, I checked all of them in the dash and under the hood, and they were all good. I pulled the main 50 amp fuse under the hood and tested voltage on the hot side. Voltage started at around 10 volts and over a couple seconds rose to 12.4 volts and held there. I then tried the same thing for the horn fuse under the hood, and it started at about 8 volts before rising to 12.4 and staying there. At this point I disconnected the negative cable and came inside. Someone suggested testing voltage between the terminals and the clamps with the headlights on to test for a bad battery connection, but this yielded no voltage. At the battery terminals, I'm getting 12.4 volts. At the battery's fuse and a bolt in my trunk, I'm also getting 12.4 volts. At this point, I'm so confused. Anyone have any ideas?

The fact that you let it sit for a week immediately makes me think the battery has become discharged. I know you say it has 12.4 volts but, I would make absolutely certain you charge that battery up. Did you try jumping it from another vehicle? I would try that stuff first. Other than that since you were working on engine mounts did you have to unhook any wiring to get at them?   Once again I would eliminate the battery as  the concern first.

I agree 100%.  Sounds like the battery has a shorted cell, which may show proper voltage but as soon as a load gets placed on it, it cannot produce current.  Take the battery to a shop for testing before you waste any time trying to charge it.Support the12volt.com

Dead battery is what I was thinking right off the bat. Paul

100 bucks says you need a better ground to either the engine block or the chassis. Ok just kidding about the 1oo bucks.Tell the Snap-On guy I'm not here!

Oops, I forgot to mention that I was also working on re-installing my alarm prior to having this problem. The alarm is currently out of the car, and there are only a few wires setup for the new install so far, and I double checked all of those wires and they're all taped up and such as to not cause shorts when I hooked up the battery. I'll take the battery to a shop to get it tested. It's an Optima red top that's not even a year old, so if it's dead, I've got a warrantee on it at least. And about the ground, I've got the battery in the trunk, with the negative cable grounding on an unpainted area of the trunk floor with an unpainted large bolt going through it. It's also sealed from underneath with silicone so no moisture can get in. The car is a '94 Toyota Celica.

Did you check your engine block for ground since you were working on the mtr mounts? Tell the Snap-On guy I'm not here!

5150azn wrote: Did you check your engine block for ground since you were working on the mtr mounts?

Yes I did. It's still grounded.

Can't wait to see how this story ends... Tell the Snap-On guy I'm not here!

Me too. I'm so confused about what's going on.