actually i don't think it's a bulb problem since the aerostar with the electronic display is a led type display.
first off i would check the dimmer circuit that controls the dash brightness on the headlight switch.
If thats not it then you have a dash circuit problem related to that circuit in the dash itself.
i'm sure if you do a little searching you can find a wiring diag for that model yr. If not then a store bought manual might such as chiltons or one of those.
I'll chk and see if i can come up with something but i'm sure you could too after searching
Laterz,