engine. So in effect, they have two sides to
their circuits: the instrument power side, and
the sending unit input side.
The troubleshooting procedure is summa-
rized in the flowcharts on pages 7 and 8.
AC Resistive Loads
This category covers AC-powered resistive
loads; i.e., heating elements. These include:
- water heaters
- electric ranges and ovens
- electric space heaters
These devices have high current draws
and can develop problems over time. You can
marine troubleshooting 7If no light, confirm available
power and, of course, check the
bulb. The TDR works quite well
for checking the entire circuit,
including the bulb, in one quick
step (Chapter 3).If the bulb is OK,
the TDR will indicate
a short circuit; if
there is a broken
filament, it will
show an open
circuit.Use a multimeter to check continuity through each leg of the circuit.OLD METHODNo light or
abnormally
dim light.SYMPTOMNEW METHODLighting Circuits (1)OLD METHODSYMPTOMNEW METHODLighting Circuits (2)Voltage drop is the cause. Use a
diagnostic meter (Chapter 2) to isolate
the location of the drop in one step. The
infrared heat gun may show a hot spot in
the circuitry, which can cause excessive
voltage drop (Chapter 5).Use a multimeter to check continuity through each leg of the circuit.Bulb is
glowing but
abnormally dim.Confirm power and a good
ground at the instrument with
a basic multimeter.If no power, repair
as needed.If power and ground are OK,
check continuity of the cable
between the instrument head
and the sending unit. A
multimeter is the best tool
for this test.Once the above has been confirmed, check
the sender. (Sending units can be checked
with a digital volt-ohmmeter [DVOM], but
since values are rarely provided in manuals,
the results can be misleading.) If grounding
the sending unit wire makes the gauge go
to full scale with the power turned on, the
sender is faulty.The methods described here follow traditional procedures. Sometimes the good old DVOM is still the best way!Instrument
inoperative.SYMPTOMNEW METHODOLD METHODEngine Instrumentation (1)save a great deal of troubleshooting time by
using the diagnostic equipment discussed in
this book.
The troubleshooting procedure is summa-
rized in the flowcharts on pages 8 and 9.Battery Chargers and Inverters
AC-supplied battery chargers, inverters, and
inverter chargers have both AC and DC cir-
cuitry in the same case. They also have both
AC and DC outputs or inputs. The test equip-
ment required will be dictated by whether the
problem is on the DC or AC side.
The troubleshooting procedure is summa-
rized in the flowcharts on pages 9–11.