my 02 probably has the same controls as yours....probably.
i have worked on several air doors.
something to check first is if the lock is on. i am sure you can remember hearing the clacking of the relay when you lock and unlock the door using the keypad or the switch inside. if you have not done it, make sure you can hear that and cycle it a few times. sounds like that is probably not the case since you get it to work once in a while.
as i am sure you already know as well that there are air release valve for both inside and outside. my outside one is in the bay door to the left of the mid bode door that i have. the inside one is in my cabinet immediately to the left as you come up the steps.
on mine, the control box and relays are in that same inside cabinet at the back of it. the relays and wiring are behind a removable carpeted panel. mine is a mid door. so if yours is a front door, then i do not know where it is. all of the control wiring comes into a block of relays in that area. i dont think there were many front entry coaches in 03.
so to help me understand, does the door make a swoosh sound when you push the button or just do nothing. mine once in a while will not open or close and just make a wooshing air noise and or just go part way. that is usually the mac valve in the door mechanism under the long laminate cover. i replaced mine once and it worked for many years and now once in a while does that. if i recycle the door button sequence a time or two then it works.
lots of rambling
here is a thread that contains the wiring diagram and some other info on wiring that is the wiring that goes from the keypad to the relay cluster in that cabinet.
https://newellgurus.com/showthread.php?t...ight=essex
tom