MP-3000 Controller
110
03 Return Air Sensor Short Circuit
(Check Alarm)
• When the sensor circuit resistance is lower than
200 ohms.
• When the temperature is above 80 C (176 F).
• Indicates:
• Short circuit to sensor
• Defective or wrong sensor
• Defective relay board
• Defective cable No. 1
• Defective controller
• Check sensor resistance between pins 3 and
4 on plug J15. Resistance must be 2,000
ohms at 25 C (77 F).
• Check cable No. 1 between controller and
relay board.
04 Evaporator Coil Sensor Open Circuit
(Check Alarm)
• When the sensor circuit resistance is higher than
100,000 ohms.
• When the temperature is below -70 C (-94 F).
• Indicates:
• Open circuit to sensor Defective or wrong sensor
• Defective relay board
• Defective cable No. 1
• Defective controller
• Low evaporator coil temperature
• Check sensor resistance between pins 5 and
6 on plug J15. Resistance must be 2,000
ohms at 25 C (77 F).
• Check cable No. 1 between controller and
relay board.
• Check evaporator airflow.
05 Evaporator Coil Sensor Short Circuit
(Check Alarm)
• When the sensor circuit resistance is lower than
200 ohms.
• When the temperature is above 80 C (176 F).
• Indicates:
• Short circuit to sensor
• Defective or wrong sensor
• Defective relay board
• Defective cable No. 1
• Defective controller
• Check sensor resistance between pins 5 and
6 on plug J15. Resistance must be 2,000
ohms at 25 C (77 F).
• Check cable No. 1 between controller and
relay board.
Alarm Codes, Descriptions and Corrective Actions (Continued)
Code Description Corrective Action
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