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Definition of Open or Short Circuit of Sensor (Thermistor)
OPEN - A lead wire is broken or disconnected or the circuit inside the temperature sensor is open.
SHORT - The protective cover of a lead wire has been damaged, and the exposed wire is touching another metal part, or both
lead wires have become exposed and are touching each other. Alternatively, the circuit inside the temperature sensor is closed.
IF A SENSOR IS DEFECTIVE
Indoor coil temp. thermistor (TH1) is defective.
Operating lamp on indoor unit is fla-
shing on and off (
*
).
Thermistor (TH1) is difective.
(That is, sensor is short).
Replace thermistor.
Function of freeze prevention conti-
nues to work in cooling mode.
Thermistor (TH1) is not connected
to indoor PCB Ass’y, or its tempera-
ture sensor is defective. (That is,
sensor is open).
Replace thermistor.
YES
YES
YES
YES
NOTE
Alarm signal - Operation lamp is flashing on and off
Operation lamp on indoor unit is flashing when the air - conditioner is in the following conditions:
●
When the thermistor (TH1) is defective (short).
In this case the compressor will stop and the indoor unit will operate only for ventilation.
●
Fault with serial communication between the two controllers (PCB1/PCB2) (ground fault
on connecting wires).
●
When the air - conditioner is submit to an high magnetic noise (electronic locking of
microprocessor).
To restore normal operation turn - off electric supply for 60 seconds at least, by discon-
necting the wall plug, then start again the air - conditioner.
Temperature
sensor
Leads
wires
Room temp. thermistor (TH2) is defective
Open
When thermistor opens, the air conditioner will be in the following conditions as the controller tries to defect extremely low room
temperature.
Short
When thermistor short, the air conditioner will be in the following conditions as the controller tries to defect extremely high room
temperature.
IN COOLING MODE - The air conditioner soon stops and will not start again. (Thermo. OFF).
Neither outdoor fan nor compressor runs.
IN HEATING MODE - The air conditioner continuer to perate. (Thermo ON). Both the outdoor fan and compressor do not stop.
As a result, the room becomes too warm.
IN COOLING MODE - The air conditioner continues to operate. (Thermo. ON).
Both the outdoor fan and compressor do not stop.
As a result, the room becomes too cold.
IN HEATING MODE - The air conditioner soon stops and will not start again. (Thermo OFF). Neither outdoor fan nor compres-
sor runs.
NOTE
I
