971 StarCool Alarm Codes And Actions

971	Sensor bus sup LO
Description	Supply voltage sensor bus low
Cause	Indication of controller voltage reference fault
Trouble shooting	Possible causes: Defective 12V power supply on main controller. Defective main controller. Short circuit on sensor Accompanied alarms: There may be sensor alarms (AL302) AL 801 will be activated during FT- or PTI test. Trouble shooting: Check if there are other active (sensor) alarms. Clear these alarms fi rst using their trouble shooting. Access the “special menu” by pressing "spanner icon" for more than 3 sec. Scroll down until you see the label “U sensor bus” in the display. The value of “U sensor bus“ should be in the range between 11 and 14V DC. While displaying “U sensor bus“, remove the connector at Pspar. − If “U sensor bus” is now inside the correct above range (11 – 14V DC), the RH and or CO2 sensor is defective. Replace the sensor(s) connected to sensor bus cable. − If “U sensor bus” is still outside the above range, proceed to next step. While displaying “U sensor bus“, disconnect sensor from the terminals according to wiring schematics inside in the control cabinet. − If “U sensor bus” is now inside the above range the cable for the RH and or CO2 sensor(s) is defective. Mount connector correctly or replace connector cable for RH and or CO2 sensor(s). − If the correct voltage is measured at X10 then circuit is defective. Replace the main controller.
Criteria	Reference voltage U sensor bus below 11V DC