99 5psd Won’t Start!
 

I'm experiencing difficulties starting my car despite installing multiple brand new batteries. I've removed the alarm control unit, checked fuses, attempted to jump-start, and cleaned the terminals. The car got wet inside due to a clogged drain plug, but after inspecting the ACU, I found minimal corrosion. Even after cleaning the ACU, the issue persists. Two days ago I had the same problem, cleaning ACU plugs and battery terminals solved the issue. In addition to this I have been unplugging the battery because the dash stays lit, leading to battery drain. This morning I went to fill the car up with gas and initially it was not starting so I tightened up the terminals and was able to start the car, it was barely running, smoking, and in limp mode with the cel flashing,I attributed this to the aos which I just recently replaced and kept driving, the car stopped struggling the smoke went away and began to run smooth. I drove to the gas station and turned off the car when I tried to turn it back on it would only click but not attempt to turn over. Currently when trying to start the car I hear one click and a faint high-pitched noise when attempting to turn, with slightly dimming headlights when turning the ignition. I plan to install a newly purchased ignition switch. Any other suggestions starting to get desperate?