Coolant Temperature Reads Inaccurately (AEROSTAR)

Measure voltage between ground and load side of fuse No. 18 located in instrument panel fuse panel. If battery voltage is present, go to step 3). If battery voltage is not present, go to next step.
Measure voltage between ground and feed side of fuse No. 18. If battery voltage is present, replace fuse and retest system. If battery is not present, repair open wiring to fuse panel and retest system. See WIRING DIAGRAMS .
Partially remove instrument cluster leaving connectors connected. See appropriate INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Turn ignition on. Measure voltage between ground and instrument cluster connectors C250, terminal No. 12 and C251, terminal No. 13 (all Red/Yellow wires). See Figure . Also inspect instrument cluster for damage. If battery voltage is present, go to next step. If battery voltage is not present, repair open in appropriate Red/Yellow wire and retest system.
Turn ignition off. Measure resistance between ground and instrument cluster connectors C250, terminal No. 13 and C251, terminal No. 9 (all Black/White wires). See Figure . If resistance is less than one ohm, go to next step. If resistance is more than one ohm, repair open in appropriate Black/White wire. See WIRING DIAGRAMS .
Perform TEMPERATURE GAUGE TEST under COMPONENT TESTS. If temperature gauge operates properly, replace coolant temperature sending unit. If temperature gauge does not operate properly, go to next step.
Using an ohmmeter, check sending unit circuit wiring and instrument cluster printed circuit for shorts or opens by physically flexing the wiring and observing continuity. Continuity reading should not fluctuate. If wiring and flex circuit are okay, replace temperature gauge. See GAUGES under REMOVAL & INSTALLATION. If wiring and flex circuit are faulty, repair wiring or replace instrument cluster. See WIRING DIAGRAMS .