1984 Ford Crown Victoria my speed sensor

The vehicle is fitted with a speedometer cable not a sensor.

The cable controls speedometer function on guage. The sensor if for cruise control !

SPEED SENSOR (EXCEPT ELECTRONIC SPEEDOMETER)
Disconnect speed sensor connector and connect an ohmmeter between wire connector terminals at speed sensor end. A reading of 200-3- ohms should be obtained.
A reading of 0 ohms indicates a shorted coil, and a high reading indicates an open coil. If reading is within proper range and speedometer operates properly, sensor is probably good. Substitute a new sensor if necessary to check operation.
SPEED SENSOR (ELECTRONIC SPEEDOMETER)
Models with electronic speedometer do not use a separate speed sensor, but are connected directly to the speedometer itself. To test, raise and support the rear of vehicle so wheels can turn.
Connect an AC voltmeter to the Dark Green/White lead, and ground at the amplifier. With speedometer indicating 30 mph, voltmeter should read between 6 and 24 volts.