Checking the Display Messages
The first area to check whe n troubleshooting the 19XL is the LID display. I f t he al arm light is
flashing, check the primary and secondar y message lines on the LID default screen (Figure 13).
These messages will in dic a te where the fault is occ ur r in g. The Alarm History t abl e 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 lig ht starts to flash while acce ssing a menu
screen, depress EXIT to return to the Default screen to read the failure message. The
compressor wil l not run with an alarm condi tion existing, unless the ala rm type is an
unauthorized start or a failure to shut down.
Checking Temper a t ur e Sen sor s
All temperature sens or s ar e of the thermistor type. Thi s means that the resistan ce of the
sensor varies with temperature. All sensors have the same resistance characteristics.
Determine sens or temperature by measuring vo ltage drop if the controls ar e powered, or
resistance if the cont r ols ar e powered off. Compare the readings to the values list ed in Table
11A or Table 11B.

Resistance C heck

Turn off the control po wer and disconnect the terminal plug of the sensor in question from the
module. Measure sensor resista nce between rec eptacles designated by the wiring diagram with