Golf L4-1588cc 1.6L DSL SOHC Turbo (1985)
Audible Warning Device: Description and Operation
DYNAMIC OIL PRESSURE WARNING SYSTEM
The components of the dynamic oil pressure warning system are the pressure switches, the electronic control unit, the low oil pressure indicator, and the
warning buzzer. A 0.3 bar pressure switch provides warning when the oil pressure falls to near zero at any time, including at idle. The other (1.8 bar)
pressure switch provides earlier warning, at elevated rpm, whenever oil pressure falls below a minimum safe level.
The low pressure switches are located on the oil filter flange (0.3 bar) and on the end of the cylinder head (1.8 bar). The electronic control unit is located
behind the instrument cluster.
CAUTION: If the warning indicator stays on after the engine is started, or flashes on while driving, always assume that there is insufficient oil pressure.
Check oil level and test oil pressure before proceeding with tests of the warning system.
Checking Low Oil Pressure Warning System
With the ignition off, the low pressure (0.3 bar) switch is closed (complete circuit to ground). When the ignition is turned on, the indicator flashes (no
oil pressure). When the engine is started and oil pressure rises, it opens the switch (opening the ground circuit), and the indicator goes out. With
insufficient oil pressure or a stuck switch, the indicator will continue to flash. The switch opens and closes at specific pressures.
To quick-check the pressure switch, simulate a closed switch by removing the blue/black wire and grounding it. With the ignition on, the indicator
should flash. If not, the problem is in the circuit or the indicator. If the indicator flashes only when tested in this way, replace the switch.
If the indicator flashes with the engine running, and the oil pressure tests OK, remove the blue/black wire from the switch with the engine running. The
indicator should go out. If not, the circuit is shorted to ground between the wire and indicator. If the indicator does go out, the switch is stuck closed
and should be replaced.
Checking Dynamic Oil Pressure Warning System (high rpm)
The 1.8 bar pressure switch is normally open (no circuit to ground). When the engine is running above 2000 rpm (ignition distributor input to control
unit), oil pressure closes the switch (completing the circuit to ground). If oil pressure is insufficient to close the pressure switch, or the switch is stuck
open, the indicator will flash and the buzzer will sound. The pressure switch opens and closes at specific pressures.
To quick-check the pressure switch, raise the engine speed above 2000 rpm and disconnect the yellow wire from the switch. The indicator should flash
and the buzzer should sound. If the wire is connected to ground, the warning should stop. Disconnect the wire from ground and connect it to the
switch. If the indicator does not go out, replace the switch.
Testing Oil Pressure Switches
The oil pressure at which the pressure switches react can be tested by temporarily installing an oil pressure gauge in parallel with the switch with a
T-fitting and monitoring switch performance with a multimeter or test light.
