Westerbeke 9.0 BCG Technical Manual page 30

Troubleshooting the Water Temperature and Oil Pressure Gauges
Given a presumably faulty gauge indication while the instrument panel is energized, the first step is to check
for 12 volts DC between the ignition (B
+ )
and the negative (B -) terminals of the gauge. Assuming there are
12 volts as required, leave the instrument panel energized and perform the following steps.
1. Disconnect the sender wire at the gauge and see if the gauge reads zero, the normal reading for this
situation.
2. Connect the sender terminal at the gauge to the ground and see if the gauge reads full scale, the nor-
mal reading for this situation.
If both of the preceding gauge tests are positive, the gauge is OK and the problem lies either with the con-
ductor from the sender to the gauge or with the sender.
If either of the gauge tests are negative, the gauge is probably defective and should be replaced.
Assuming the gauge is OK, proceed as follows. Check the conductor from the sender to the sender terminal
at the gauge for continuity.
Check that the engine block is connected to the ground. Some starters have isolated ground terminals, and
if the battery is connected to the starter (both positive [
+ ]
and negative
[-n,
then the ground side will not
necessarily be connected to the block.
If the sender to the gauge conductor is OK and the engine block is grounded, the sender is probably defec-
tive and should be replaced.
Connecting Pressure SenSing Devices to Oil Galleries
Oil pressure senSing devices, such as senders and switches, must never be connected to any oil gallery of
an engine with the use of tees or extended nipples. The reason is simply that continued engine vibration
causes fatigue of the fittings used to make such a connection. If these fittings fail, the engine loses its oil
and oil pressure and internal engine damage may result.
Such pressure sensing devices must be bulkhead-mounted and connected to the oil gallery using an ap-
propriate grade of lubricating oil hose. Any fittings used to connect the hose to the gallery must be of steel
or malleable iron composition. Brass must not be used for this application.
Westerbeke Generators 24