Bosch L-Jetronic Electronic Fuel Injection

Fig. 6 Thermo coolant time switch resistance check:

1. Remove thermo coolant time switch and plug opening to prevent loss of coolant.
2. Check that switch is fully cooled by placing in cold water.
3. Connect test lamp between battery positive terminal and switch terminal. Connect second wire between battery ground terminal and switch body. Test lamp should light.
4. With test lamp still connected, place switch in water, then heat water slowly.
5. Lamp should go off when temperature of water reaches 88-102°F (31-39°C). Nominal values of switch are marked on switch body.
6. Check resistance of switch using ohmmeter connected between pins W and G and ground, Fig. 6.
7. If switch is lower than 86°F (30°C) with ohmmeter connected between terminal G and ground, ohmmeter should read 25-40 ohms. If switch temperature is greater than 104°F (40°C) ohmmeter should read 50-80 ohms. With ohmmeter connected between terminal W and ground and switch temperature below 86°F (30°C), ohmmeter should read zero ohms. With switch temperature above 104°F (40°C), ohmmeter should read 100-160 ohms. With ohmmeter connected between terminals W and G and switch temperature below 86°F (30°C), ohmmeter should read 25-40 ohms. With switch temperature above 104°F (40°C), ohmmeter should read 50-80 ohms.