Sensor Checks

These include, in particular, the oil pressure switch and the brake fluid and coolant level switch.

CHECKING

1. Connect a test lamp or ohmmeter to the switch terminals. To do this, disconnect the cables from the switch.

* Switches screwed into the cylinder block generally do not have a ground cable, as the ground connection is made through the housing.

2. When the switch is closed, the tester should show a reading. The ohmmeter is the best tool for this purpose. When the switch is closed, the ohmmeter should read 0 ohms; when open, infinity ohms.
3. The function of the coolant level switch and brake fluid level switch is easiest to check as follows. With the ignition on, disconnect the wire from the switch and connect it to a reliable ground point, for example the cylinder block. If the corresponding warning indicator on the instrument panel illuminates, the switch is faulty.
4. The oil pressure switch is a special case. With the engine off, the contact is closed (indicator lit). The switch opens only at a specific oil pressure.