THERMO Time Switch

Using a thermometer, check engine coolant temperature. Compare coolant temperature with value stamped on thermo time switch body. Connect an ohmmeter between terminal "W" on switch and ground.
If coolant temperature is higher than switch value, a very high resistance denoting an open circuit should be obtained.
If coolant temperature is lower than switch value, a very low resistance denoting a closed circuit should be obtained. If switch does not respond as outlined, replace thermo time switch.
If switch passes resistance test, allow coolant temperature to cool below stamped value on switch. With ohmmeter connected, connect battery power via an isolating switch to terminal "G".
Using a stop watch, check delay time as ohmmeter changes between high and low resistance. Delay period should be as specified. See Coolant/Delay Time Relationship chart. If not, replace thermo time switch.

COOLANT/DELAY TIME RELATIONSHIP