Thermo-Time Switch

Resistance between terminal “W” on thermo-time switch and ground

The required resistance values differ between thermo-time switch models.

The resistance should reach 0 Ohms (continuity) with engine temperature below:

Bosch part no. Temperature (F) Temperature (C)
0 280 130 219 50 10
0 280 130 221 56 13
0 280 130 214 86 30

The resistance should rise to infinity with engine temperature above: Infinite resistance with engine temperature above:

Bosch part no. Temperature (F) Temperature (C)
0 280 130 219 68 20
0 280 130 221 74 23
0 280 130 214 104 40

If resistance value lies outside of specification, thermo-time switch is defective.