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4-2
BASIC Electrical Troubleshooting
Whenever testing for power (voltage)
fl
ow in the circuit, the FIRST order of business is to establish and verify the test unit
is functioning properly and has a solid ground. When possible, attach the ground lead of the tester directly to the ground
post of the battery pack. Using the positive lead of the tester, probe the positive terminal of the battery pack and “verify”
that the tester, and your connections, are working properly.
We are about to provide you with a simple, step-by-step process that will let you divide and conquer common DC circuit
problems. It is called a voltage drop test, and it works! Voltage drop tests are an e
ff
ective way to test an electrical circuit’s
ability to deliver power to electrical loads.
THE NATURE OF CIRCUITS
Circuits and power supplies exist for one reason: to supply electrical power to operate loads.
Voltage drop causes countless unsolved electrical mysteries, especially when it infects the ground side of a circuit. It can
also trick you into replacing parts that are not in need of replacement.
The more connections and wiring a unit has, the more vulnerable the electrical system is to voltage drop
.
VOLTAGE DROPS-GOOD OR BAD?
Voltage drop tests are usually performed to test loads and locate circuit problems. As a result, we may have a tendency
to think of voltage drops as bad things. But voltage drops can be good or bad; it all depends on where they occur in the
circuit, and whether they operate loads or simply waste energy.
GOOD
voltage drops are essential. Loads won’t work without them. Available voltage must be dropped across the load,
or it cannot work.
BAD
v
oltage drops allow available voltage to be “dropped” at a high resistance elsewhere in the circuit; this steals electrical
energy from the load. A bad voltage drop in a circuit converts electrical energy into heat.
RULES OF CIRCUITS
Let’s agree on the following rules:
1) CIRCUIT CURRENT IS DETERMINED BY THE LOAD(S).
A 75-watt bulb demands less current than a 100-watt bulb
screwed into the same socket. Installing a higher wattage bulb increases the circuit load. Adding a second light to a circuit
also increases the circuit load. Adding loads increases circuit current. Circuits are designed to supply a speci
fi
ed amount
Single battery test (6 plus volts reading)
Battery pack test (24 plus volts reading)
