Carrier 38EV024320 User Manual
Page 17
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ERROR CODE #3 - OUTDOOR THERMISTOR FAILURE
ERROR CODE #4 - SUCTION THERMISTOR FAILURE
REASON:
CONTROL BOARD READS THERMISTOR TEMPERATURE ABOVE 160T OR BELOW -40T.
POSSIBLE CAUSES:
Reference Figure 21
1) Thermistor failed or out of calibration (see Note 1).
2) Loose or corroded connection.
3) Faulty control board.
Notes:
1) If thermistor is out of caiibra:tion, it may read accurately when system Is off, but may drift from actual
temperatures during operation.
2) COOL MODE: Monitor temperature at unit service valves.
HEAT MODE: Monitor temperature inside unit at thermistor location.
3) Adjust thermostat 4°F or more above or beiow room temperature, depending on mode, to force system
to high speed.
4) if unit has been off a short time, allow refrig, temperatures to stabilize.
A87475