Carrier NDK33BN0KB, Operation & Service Manual

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62-61753-21 7-95
Alarm
NO.
Steps ALARM / CAUSE CORRECTIVE ACTION
249 MICROPROCESSOR ERROR

TRIGGER-ON: Microprocessor Input Conversion Error.

UNIT CONTROL: Shutdown and alarm.

RESET CONDITION: Auto Reset when input conversions are valid, or Alarm may be manually
reset by turning the unit off, then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (see reset condition above). Operate the unit through the appropriate modes to see if any
active alarm occurs. Continue with the steps below as necessary.
1 Check Microprocessor
a. Check Temperature Sensor Data Must be valid reading for RAT, SAT, AAT, etc.
b. Check for any Active Sensor
Alarms
Must all be cleared.
2 Check Microprocessor & Unit Wiring
a. Check Wiring to Micro and at input
devices to the micro.
Must not be miss wired to allow 12 VDC on any of the
sensor input circuits.
3 Reset Microprocessor
a. Turn START/RUN-OFF switch off
for 30 seconds, then turn back on.
Microprocessor powers up OK
b. Alarm 249 remains active. Replace microprocessor. Refer to Section 5.4