Electronics International CGR-30P - Manual (Page 63)

The voltage on the open signal wire should measure bus voltage.
Short the signal wire to ground. Check the sensor counts go to a low (or high,
depending on the float type) reading.
2. Problem: The Resistive Float does not operate properly.
a) Action: With the signal wire removed, measure the resistance of the float. This should not
be done with a full or empty tank but somewhere in-between. Record the resistance
reading and the variations. Lift the wing and allow it to return to its original posi-
tion. Record the resistance reading and the variations. This test can be done at
different fuel levels. If the resistance value does not return to its original value, you
may have a defective Resistive Float.
Symptom: Symptom: Symptom: Symptom: Symptom: The sensor counts decrease as you add fuel.
1. Problem: The probe selected in the “Function Configuration" screen may be the wrong probe.
a) Action: Check the Probe selected in the “Function Configuration” screen. The “RFLM-4
H=F” probe should be used on Resistive Floats where high resistance = full tank
readings and the “RFLM-4 L=F” probe should be used on Resistive Floats where
low resistance = full tank readings.
7.9 Capacitive Fuel Level Problem:
Fuel can be measured in a fuel tank using a Capacitive Fuel Probe. The Electronics International P-300 Ca-
pacitive Fuel Probe connects to an IMC (Interface Module) located near the probe, and to the EDC through
three wires. Power (+5 volts) is supplied on the Red wire, ground is supplied on the Black wire and the fuel
level signal (a 0 to +5 volt square wave) is supplied (by the P-300C) on the White wire.
As the fuel level in the tank increases, the capacitance of the probe increases. The IMC Module converts the
capacitance to a frequency. The higher the fuel level, the lower the frequency of the square wave on the White
wire.
The EDC monitors the signal and produces a digital value (called sensor counts) based on the signal frequency.
The sensor counts can be viewed in the “Function Mapping” screen. The sensor counts are then converted to a
fuel level based on the calibration data in the “Function Mapping” screen.
Symptom: Symptom: Symptom: Symptom: Symptom: Inaccurate, jumpy or zero reading.
1. Problem: The IMC is mis-wired.
a) Action: Measure the voltage on the three wires at the IMC Module (Red wire = +5 volts,
Black wire = ground, White wire = +2.5 volts).
Remove the Red wire from the IMC module and check the sensor counts on the
“Function Mapping” screen to increase. Be sure you are displaying the data for the
correct tank.
Touch the outside of the wires between the IMC Module and the probe and check
that the sensor counts increase.
5 4