This car lived in Phoenix until 2 years ago. It was, and is, well maintained. 2 years ago I moved to Houston (very humid). About 6 months ago, after about 5 days of solid rain (car sitting outside), I jumped in and all hell broke loose. I noticed that when I opened the door, the door locks went off on their own, The car started and I pulled out of the driveway. I noticed the headlights and interior lights were dim and the digital clock was flickering. When I turned on the radio, the transmission downshifted. When I opened the window, the lights went off. When I turned on the a/c, the engine sputtered. Like an idiot, I still got on the highway, and the car was sputtering and downshifting, slamming all the way from 4th into first and back, and the radio, a/c switch, and windows all seemed to be having effects on the engine, and transmission. I made it to about 3 blocks from home and the car died at a stop sign. Battery now dead. I left the car there for 4 days. I kept trying to start it every day. Finally, on the 5th day, it started (with a jump, of course). I assumed that water had leaked into the computer, but it was not wet. After some reading, I replaced both the alternator (OEM Denso) and the battery. All was fine until a few days ago. I was now garaging the car, but it again had rained for a few days, and the car sat in a damp garage. When I tried to start it, the battery was dead. The sun was out, so I parked it outside, and charged the battery. Next day, I drove to the store. Guess what!....Same ole ****, windows, a/c, lights, transmission, all going bat **** crazy. Same downshifting and sputtering. This time, I immediately drove home, parked the car in the garage, put one dehumidifier in the garage, and the other one in the car. Let them run for 2 days. Still no good. Now my battery won't hold a charge, the alternator is not charging. How can that be since both are new?

I only get 12.1 volts on the battery at rest, and the same with the car running, and if I park it overnight, the battery loses charge, I did basic parasitic draw test (battery post to body and engine...nothing. Again, basic tests from alternator to battery post, nothing. Alternator plugs are connected, belt is tight, alternator is new (the old one was probably fine)

The weird thing is that it was never water getting in the car from above, it's humidity getting in somewhere that's causing the issue. But where? and why is it taking so long to dry out?

WTF?....gotta be the computer, a fuse, or a short, right? Can anyone help me with a diagnosis procedure?

Does the computer have any control over the charging system?

Oh, by the way, my Ebrake light is now illuminated on my dashboard when it is not engaged....just happened.

Maybe it's haunted.

 

Check all your ground points to the body, check the wire harness in the doors to make sure nothings pinched. Another option would be to see if someone installed an aftermarket security or remote start system. When you have that many oddities chances are that it's a wire harness/ground issue.

My money is on someone hacking up wiring and not having the patience to do the job right.

 

Agreed, a ground short is the most likely suspect...but the parasitic drain test should identify that issue. One thing I have noticed is that the seat belt for the driver side seems to get wet (in the body spool), when it rains....and the left rear door speaker has stopped working. Probable water leak in that area, although I cannot see it....I took that area apart and did not see anything...

 

A ground issue may not show up until power is given in a specific way. There are so many ways errant electricity could wind up where it shouldn't. I would also look out for chewed wiring, rats are a blight upon the earth I swear.

 

I just had a thought. I know it sounds silly but check your brake light bulbs and flashers. When I had one fail partially, I had all sorts of weird electrical issues. If one of the dual filaments partially falls onto the other, you could have power shorting backwards into the system.

 

Water leak might be coming through the weatherstripping around the sun roof. I think item #1 is figure out what is leaking. That will help tracing the electrical issues.