Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

1. Disconnect electrical connector and remove sensor or switch.
2. Immerse sensor element in temperature controlled solution.
3. Test combination pre-heat/temperature gauge sensor as follows:
a. Connect ohmmeter between pre-heat terminal on sensor and metal sensor housing. Sensor terminals are arranged in an ``L'' shape. Pre-heat terminal is lower terminal and temperature gauge terminal is vertical terminal.
b. Sensor resistance should be:
1134 ohms at 68°F
704 ohms at 86°F
272 ohms at 140°F
114 ohms at 194°F
c. If meter readings are not within 10% of specified values, sensor is defective.
4. Test VP-20 coolant sensor as follows:
a. Connect ohmmeter between sensor terminal and metal sensor body.
b. Sensor resistance decrease progressively from 2400 - 3000 ohms at 68°F to 300 - 500 ohms at 172°F.
c. If resistance values are not as specified, or if sensor performance is erratic, sensor is defective.
5. Test EGR temperature switch as follows:
a. Connect ohmmeter to switch terminals and slowly heat sensor element.
b. Meter should indicate no continuity below 167 - 177°F, and should indicate continuity above 177 - 177°F.
c. Cool sensor element while observing ohmmeter.
d. Meter should indicate continuity above 145 - 135°F, and should indicate no continuity below 153 - 145°F.
e. If switch fails to perform as outlined, switch is defective.