Reset Conversion Constant: Aerostar

Use the following steps to program a new speed conversion constant for conventional cluster.

1. Locate PSOM conversion constant service wire underneath instrument panel. This is a single terminal ground wire, Circuit 571 (Black/Orange wire).
2. Insert a metal clip in service wire connector and clip other end to vehicle ground while ignition switch is in OFF position.
3. Turn ignition switch to RUN (not crank) position while holding down trip odometer RESET button on speedometer. Release RESET button.
4. The speedometer will prove out (sweep across dial and back). The English/metric and revision levels will be displayed.
5. Press and release RESET button again and PSOM conversion constant (without the decimal point) followed by word "CAL" will appear.
6. Press and release odometer SELECT button as many times as is necessary to change conversion constant to correct value. The count can be changed to display all possible values.
7. When correct new value is displayed in odometer window, press and release RESET button to lock in new conversion constant.
   NOTE: Doing this reduces maximum number of times PSOM can be re-programmed by one count. The module can only be re-programmed three times. If you change your mind and want to go back to old conversion constant, turn ignition switch off before you lock in new constant.
8. Turn ignition switch off and remove ground wire. Verify proper operation.