Oil reservoir and oil-level switch

The oil reservoir contains an oil filter and an oil-level switch with float. In contrast to the oil-level switch, the oil filter cannot be replaced separately. A dipstick designed to allow checks of the fluid level is attached to the screw-on cap.

The oil-level switch detects whether the required oil level in the oil reservoir is exceeded or undershot. The VDM control unit sends the signal on the bus system to the instrument panel. The instrument panel issues a Check Control message. Normal motion of the oil in the oil reservoir does not lead to a Check Control message.

There is a permanent magnet in the moving float; this triggers the reed contact in the oil-level switch firmly fitted in the reservoir. Here, the reed contact converts the float movement into an electrical signal. The Reed contact remains closed when the fluid level is above "minimum" (roughly 10 mm below the "minimum" graduation).

Fig 1: Identifying Oil Reservoir And Oil-Level Switch

Courtesy of BMW OF NORTH AMERICA, INC.

On the oil-level switch, short circuit or line disconnection cannot be detected. A line disconnection is interpreted as oil loss. A short circuit is not detected.