Carrier 17/19EX - Manual (Page 255)

Checking the Display Messages
The first area to check when troubleshooting the 17/19EX is the LID display. If the alarm light
is flashing, check the primary and secondary message lines on the LID default screen ( Figure
14 ). These messages will indicate where the fault is occurring. The Alarm History table on the
LID Service menu will also carry an alarm message to further expand on this alarm. For a
complete listing of messages, see Table 8 . If the alarm light starts to flash while accessing a
menu screen, depress EXIT to return to the Default screen to read the failure message. The
compressor will not run with an alarm condition existing, unless the alarm type is an
unauthorized start or a failure to shut down.
Checking Temperature Sensors
All temperature sensors are of the thermistor type. This means that the resistance of the
sensor varies with temperature. All sensors have the same resistance characteristics.
Determine sensor temperature by measuring voltage drop if the controls are powered, or
resistance if the controls are powered off. Compare the readings to the values listed in Table 9A
or Table 9B .