TM 1-2840-252-23-3
G-3 TEST EQUIPMENT
a. Some fault isolation procedures require the use of a volt-ohmmete to indicate resistance across the wire
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harnesses or across component connector pins. To avoid unstringing harnesses, use test cables with size 20
pins to mate with the harness plugs and sockets.
b. The voltmeter used for measuring voltages shall have an accuracy of 0.1 percent full scale or better on the
200V range.
c.
The ohmmeter used for measuring all resistances except ground strap resistance shall have an accuracy of
0.05 percent full scale or better on the 2000 range and 0.5 percent full scale or better on all other ranges. The
ohmmeter used for measuring ground strap resistance during the insulation/voltage check shall be capable of
measuring 50mΩ with an accuracy of 5mΩ, using a four wire configuration. The meter should always be set
to the lowest possible range for the specified limits. If the autoscale function is used, an automatic switch from
one range to another can appear to be a discontinuity in the component being measured. If this occurs, turn
off the autoscale function and manually set the meter to the appropriate range.
CAUTION
DO NOT USE A METER THAT WILL SUPPLY MORE THAN 5mA WHEN MEASURING PLA OR
METERING VALVE POTENTIOMETER RESIS- TANCES (FAULT CODES B7, F4 AND F6) AS THIS
CAN DAMAGE THE POTENTIOMETER.
G-4 RESISTANCE AND INSULATION TESTS
a. Components which fail the resistance and insulation test specified herein are suspected to be faulty. Consult
the manufacturer's procedure for diagnosis and troubleshooting of these components before replacing. Note
that conductive solvents may cause temporary resistance and insulation shorts or failure. If wetting is a
possible cause of the problem, allow the affected component to dry out, then recheck the resistance.
G-5 HIGH FUEL CONSUMPTION
a. The engine HMA cannot cause high fuel consumption. Fuel consumption depends upon turbine engine
condition, fuel characteristics or operating conditions. No troubleshooting of the HMA system is required.
G-2
