Town Car V8-302 5.0L (1987)
Vehicle Speed Sensor: Testing and Inspection
Speed Control/Speedometer
Speed Signal Test
Speed signal test
Electronic Instrument Cluster Only
1.
With wheels raised and vehicle speed at 30 m.p.h., measure the AC voltage of the speed signal at the speed control amplifier connector, Fig. 10.
2.
If reading obtained is less than 6 volts, disconnect speed control amplifier and repeat measurement.
a. If voltage is greater than 6 volts, replace speed control amplifier and retest.
b. If voltage obtained is less than 6 volts, check circuit 150 back to speedometer stud on the cluster for an open or short. If circuit is satisfactory,
replace speedometer electronics and retest. If an open or short exists, repair as necessary.
3.
If reading obtained is more than 6 volts, measure the DC component at the speed control module.
a. If voltage obtained is greater than 1 volt, replace speedometer electronics and retest.
b. If voltage obtained is 1 volt, speedometer circuit is satisfactory. Proceed with ``Speed Control Diagnosis.''
Speed Sensor Test
ANALOG INSTRUMENT CLUSTER
1. Disconnect electrical connector from speed sensor and connect an ohmmeter between the speed sensor terminals at speed sensor end.
2. A reading of approximately 30---100 ohms for 1982 models and 1983 Escort, EXP, LN7 and Lynx or approximately 200---300 ohms for
1983---87 models should be obtained. A reading of 0 ohms indicates a shorted coil and maximum reading indicates an open coil.
3. Replace the sensor if a correct reading has not been obtained.
