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1. Problem: The Power or Ground wire is open or not connected properly.
a) Action: Measure the voltage on the power and ground wires. Ohm the ground wire to
ground. Look for a short.
B. Symptom:B. Symptom:
B. Symptom:B. Symptom:
B. Symptom: “COM” is displayed for the digital value for most functions. The EDC is not communi-
cating with the CGR.
1. Problem: One of the EDC external +5 volt power supplies on the Bottom Connector is shorted
to ground.
a) Action: Remove the Bottom Connector. If the COM error goes away, look for a short
on one of the +5 volt wires.
2. Problem: The Power or Ground wire to the EDC is open or not connected properly.
a) Action: Measure the voltage on the appropriate EDC pins. Ohm the Black ground wire
to ground.
3. Problem: The EDC +10 volt or one of the +5 volt supplies on the Top Connector is shorted to
Ground.
a) Action: Measure the +10 volt and +5 volt supplies on the Top Connector. If one of the
voltages is low, use an ohmmeter to find the problem. If all wires ohm properly
(>100 ohm when disconnected from the EDC), the Power or Ground wire to the
Top Connector may be open.
4. Problem: The 5V-Serial wire from the EDC to the CGR may be open.
a) Action: Inspect the wire. Remove the connectors from the EDC and the CGR and check
for continuity.
Symptom:Symptom:
Symptom:Symptom:
Symptom: “REF” is displayed for the digital value for all temperature functions.
1. Problem: The Middle Connector on the EDC is loose or not connected. The Reference Diode
on pins 10 and 28 of the EDC Middle Connector is damaged. Note: Pin 28 should
measure 0 volts and pin 10 should measure around .6 volts.
a) Action: Inspect the EDC Middle Connector and measure the voltage on pins 10 and 28.
Symptom:Symptom:
Symptom:Symptom:
Symptom: “OVR” is displayed for the digital value for a function.
1. Problem: If a channel on the EDC is over ranged (>2.5 volts between the “+” and “-” inputs),
an “OVR” will be displayed for that function. This can happen on a channel that is
used to monitor an Annunciator, Flap or Trim function. The max input voltage for
any temperature or pressure channel is +5 volts to ground. The maximum differen-
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