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

Coolant Temperature Sensor:

1. Disconnect battery ground lead (battery is in trunk).
2. Carefully remove cooling system cap. If system is very hot, wait until engine cools sufficiently to reduce cooling system pressure. Measure coolant temperature with a suitable thermometer.
3. Unplug sensor connector and connect ohmmeter across sensor terminals.
4. Ohmmeter reading should closely approximate values on table below.
5. Check resistance between each sensor terminal and ground. There should be no continuity.
6. If resistance reading varies excessively from table or continuity exists between either terminal and ground, replace sensor.

Temperature / resistance relationship is as follows:

TEMP (°F / °C) OHMS

50 / 10 4.4K
68 / 20 2.5K
86 / 30 1.6K
104 / 40 1.2K
122 / 50 840
140 / 60 630
158 / 70 470
176 / 80 320
194 / 90 210