Electronics International MVP-50T - Manual (Page 57)

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Some Tach Generators have the common ends of the coils open. In this case one end of a coil should be
grounded and the other end routed to the RPM input on the EDC.
A. Symptom: A. Symptom: A. Symptom: A. Symptom: A. Symptom: Inaccurate, jumpy or zero reading.
1. Problem: Improper connection to the coil.
a) Action: Ohm the Tach Gen. pin connected to the EDC with respect to ground. It should
measure between 10 and 50 ohms. If this pin is open, you may not be grounding
the other end of the coil. Also, it's not uncommon to have a bad coil. In this case
you can select another pin (coil) on the Tach Gen. to connect to the EDC.
b) Action: The Tach Gen. can be removed from the engine and spun with a drill (be sure the
Tach Gen is grounded to the same ground as the EDC. You should see a reading
around 10 to 20%. Normally, 4200 RPM = 100% reading.
c) Action: The Tach Gen. can be removed from the engine and spun with a drill (be sure the
Tach Gen is grounded to the same ground as the EDC. You should see a reading
around 10 to 20%. Normally, 4200 RPM = 100% reading.
2. Problem: Wrong calibration data.
a) Action: Check the calibration numbers on the "Engine Data, Hour Meters and Flight Timer
Setup" screen.
7.6 7.6 7.6 7.6 7.6 Fuel Flow Problem: Fuel Flow Problem: Fuel Flow Problem: Fuel Flow Problem: Fuel Flow Problem:
Fuel Flow is measured using a Flow Transducer. Power (+10 volts on the Red wire) and ground (Black wire) is
supplied to the transducer from the EDC. A rotor in the transducer spins and produces pulses (0 to +5 volts) on
the White wire. The +5 volts portion of the pulse on the White wire comes from a pull-up resistor in the EDC.
The K-factor found in the “Add Fuel” screen calibrates the pulses to a flow rate.
A. Symptom: A. Symptom: A. Symptom: A. Symptom: A. Symptom: Inaccurate readings.
1. Problem: The K-factor is incorrect.
a) Action: Check that the K-factor (found in the “Add Fuel” screen) is correct for the trans-
ducer installed in the aircraft (FT-60 red cube = 68,000, FT-90 gold cube = 33,800
and the FT-180 black cube = 22,400).
B. Symptom: B. Symptom: B. Symptom: B. Symptom: B. Symptom: Inaccurate, jumpy or zero reading.
1. Problem: A wire is open, shorted or mis-wired.
a) Action: Measure the voltage on the transducer wires from the EDC at the Flow Transducer.
The Red lead = +10 volts, Black wire = 0 volts, White wire = + 5 volts with the
White wire removed from the flow transducer.
Ohm the Black wire to ground. The Black wire must be shorted to ground (< 10
ohms).