So I have had my 2000 Excursion for a while now and I seem to keep having this problem with the security system when it rains (sometimes). What will happen is I shut it off, walk away, and lock the doors. That's when Matilda starts having fun. the locks constantly cycle, the dome light stays on, and the security light starts flashing rapidly. If I catch all this BEFORE my batteries go dead I can still get everything to stop just by starting the vehicle, but as soon as I shut it off it comes right back. I either have to disconnect the batteries or it will go dead in a few hours. Any help, wisdom, experience, or prayers are welcome.

Just a WAG on my part;..BUT
It sounds like water has been getting into your GEM module..
You probably have a leak around the bottom of your windshield , , that's dripping into the Gem Module
First thing to do, is seal your lower windshield, then hope it may dry out ?????????????????
Other than that you may have to replace the GEM Module

Thank you it sounds like fixing the leak should work if that what is causing it. Like I said it only happens when we get a heavy rain. I can take it through a carwash and its fine but we get 4 inches or so and it does it So I will check into that.

Thanks again, I hope this works