Switch sensors — check

Sensors-switches are, for example, sensors for warning lights for the level of brake fluid, engine oil and coolant.

1. Attach a device to the sensor leads to «ringing» (test light or ohmmeter). To do this, disconnect the wires from the sensor.

Attention! Sensors screwed into the cylinder block usually do not have a wire «masses» (-), so their attachment to «mass» (-) occurs through the cylinder block, on which the body of the sensor itself closes.

When closed (included) sensor, the device should show the passage of current. For such «ringing» it is best to use an ohmmeter: when the sensor is closed, it should show 0 ohms, and when it is open, it should read ∞ ohms (infinite resistance).

The operation of switches such as the coolant or brake fluid level indicator can be checked by disconnecting the supply wire from it with the ignition on, which is then connected to «solid» «mass» (-), for example, to the cylinder block. If now the light on the instrument panel works, then the sensor is faulty.

A special case is the oil pressure sensor. When the engine is off, its contact is closed and when the ignition is on, the engine oil pressure warning light is on. And only when the engine is running, when a certain oil pressure is reached, the switch opens.