Mercury MerCruiser MCM 454 Mag MPI Service Manual page 473

MULTI-PORT FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
When a test light is specified, a "low-power" test light must be used. DO NOT use a high-
wattage test light. While a particular brand of test light is not suggested, a simple test, as
shown below, on any test light will ensure it to be safe for system circuit testing. Connect
an accurate ammeter (such as the high impedance digital multimeter) in series with the
test light being tested, and power the test light ammeter circuit with the vehicle battery.
IMPORTANT: If the ammeter indicates LESS than 3/10 amp. current flow (.3 A or 300
mA), the test light is SAFE to use. If the ammeter indicates MORE than 3/10 amp. cur-
rent flow (.3 A or 300 mA), the test light is NOT SAFE to use.
NOTE: Using a test light with 100 mA or less rating may show a faint glow when test actually
states no light.
When using a DVOM to perform voltage measurements, turn the ignition OFF when
connecting the DVOM to the circuitry to be tested.
Index
Page 5B-14
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a - Test Light
b - Battery
c - Ammeter
c
a
b
SERVICE MANUAL NUMBER 23
90-861326--1 MARCH 1999