ENSTROM F-28F/280F SERIES MAINTENANCE MANUAL SUPPLEMENT
Rev.
4
MM-21-7
Jun
21/12
PROBABLE CAUSE
REQUIRED ACTION
One indicator is dim when “press-to-test” is pressed:
One lamp burned out
Replace lamp. If no change, reinstall first lamp
and replace second lamp.
Low rotor rpm circuit, including horn, doesn’t work:
Blown fuse
Replace 1 amp fuse, in line between low rotor
signal conditioning unit and 12-volt bus.
Open circuit
Check all connections and continuity of wiring
harness
NOTE: The troubleshooting steps listed below apply to F-28F S/N 831 and
subsequent and 280FX S/N 2136 and subsequent.
Annunciator panel rotor RPM circuit, including horn and tone, doesn’t work:
Blown fuse
Replace 1 amp fuse, in line between signal conditioning unit
and bus.
Open circuit
Check all connections and continuity of wiring harness.
ROTOR RPM light does not extinguish:
Open circuit
Check connections and continuity of wiring between the
signal conditioner and the magnetic sensor.
Magnetic
sensor
improperly positioned
Remove the magnetic sensor inspection plug located on
the front of the main rotor transmission. Ensure the gap
between the ring gear and the magnetic sensor is between
0.030-0.045”/0.76-1.14 mm. Adjust the amount of shims
under the head of the magnetic sensor as required.
Replace the inspection plug.
Defective
magnetic
sensor
Using a multi-meter, check for 270-330 ohms across the
leads. Replace the magnetic sensor if the ohm check is
outside the 270-330 ohm range or if inspection of the
system components and wiring isolates the problem to the
magnetic sensor.
UNCONTROLLED COPY WHEN DOWNLOADED OR PRINTED
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