Checking the Display Messages

The first area to check when troubleshooting the 19XL is the LID display. If the alarm light is flashing, check the primary and secondary message lines on the LID default screen (Figure 13). 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 10. 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 11A or Table 11B.

Resistance Check

Turn off the control power and disconnect the terminal plug of the sensor in question from the module. Measure sensor resistance between receptacles designated by the wiring diagram with

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Carrier PC211 specifications Checking the Display Messages, Resistance Check