1992 ford econoline club wagon van alarm randomly activates

I have a 1992 ford club wagon (econoline) e150 with tow package and on a random occasion, the alarm will go off even if it is not armed. i can even hit unlock on the control to make sure the antitheft light is off in the dash and it could still sound off at any time. one night it sounded and every time i hit the unlock button on the remote you could hear the horn stop like it was going to deactivate but it immediately sounded again several times in a row. my brother and i were talking about it one day standing near my car and it went off. i deactivated it, checked all the doors were closed. left it disarmed. went back to talking and it did it again. my brother worked on fords for a year or more in the past, he was stumped. i called a local ford dealer and they said they had never heard of it and had no suggestion for me. the van can go for weeks to months without doing it and then out of the blue, it will sound off again. sometimes i can make it stop and sometimes it keeps sounding off or will do it several times in a row. i cant see any patterns as far as cold or warm weather, rainy or dry, windy or calm. alarm state, armed or disarmed. eather way, it randomly does it. the only other issue i see is that the driver door autolock doesnt work so you have to manually push it down or use the key. and how i lock it doesnt matter, either. all the fuses are good. i have thought about disabling the horn, but if the alarm triggers, you cant start the van until you disarm the alarm with the remote keyfob. even if the alarm wasnt armed to begin with. i thought about disabling the anti theft, but the fuses are all linked to something else that needs to be active. the previous owners said they never had a problem with that. also, i almost forgot to mention, sometimes the alarm will trigger when i go to start the van. it doesnt have the key chip pats system, just a standard key. but on a rare occasion i go to turn the key and when i hit the "start" position, the horn blares, lights flash and no juice to the starter. i click unlock on the remote and then it starts. i have also checked all the map lights which i do everytime i get out of the van to make sure the kids didnt turn them on and leave them. i took the van to a diagnostics shop and they ran the van, checked codes, and it even went off on them while they were moving it. and it never seems to go off if the van is running, only powered off. the diagnostics shop didnt know what to think about the alarm but suggested a thorough check because the map sensor is bad. they wanted to charge almost a grand to go in there again and see if something else is messed up causing a code for the map. they disabled the map by pulling the plug and advised it is only a temp fix. this didnt change anything either.