This is from a 98 expy owners manual. It should be the same for a 97. If you don't have an owners manual you can get it at:
http://myford.fordvehicles.com/
Just register there and you will have access.
Hope this helps
Scucci
Deactivating autolock - (Keyless entry system pad)
Before following the activation or deactivation procedures, make sure
that the anti-theft system is not armed, the ignition is OFF and all
vehicle doors and liftgate window are closed.
1. Enter the 5 digit entry code.
2. Press and release the 3/4 control
while holding the 7/8 control.
3. Release the 7/8 control.
The horn will chirp once if autolock
was deactivated or twice (one short
and one long chirp) if autolock was
activated.
To reactivate autolock, repeat steps 1 through 3.
Autolock can also be activated or deactivated using the following
procedure:
You must complete steps 1 through 5 within 30 seconds or the procedure
will have to be repeated. If the procedure needs to be repeated, you
must wait 30 seconds.
1. Turn the ignition key to ON.
2. Press the power door unlock control three times.
3. Turn the ignition key from ON to OFF.
4. Press the power door unlock control three times.
5. Turn the ignition key back to ON. The doors will lock and unlock.
6. Press the power door unlock switch. The horn will chirp once upon
successful toggling of the Autolock feature.
7. Turn ignition to OFF. The horn will chirp to confirm procedure is
complete.
