Service manual

3-4
AY-ZP35PR
2. Outdoor unit
Item Mode Control operation When resistance
is low (tempera-
ture judged higher
than actual)
Short-circuit When resistance
is high (tempera-
ture judged lower
than actual)
Open-circuit
Compressor cham-
ber thermistor
(TH1)
Cooling
Dehumidifying
Heating
Expansion valve
control and com-
pressor protection
Compressor oper-
ates, but room does
not become cool or
warm (expansion
valve is open).
Compressor high
temperatur
e error
indica
tion.
Layer short-circuit
or open-circuit may
result in compres-
sor in normal oper-
ation.
Outdoor unit ther-
mistor open-circuit
error indication.
Heat exchanger
thermistor (TH2)
Cooling
Dehumidifying
Outdoor unit heat
exchanger over-
heat prevention
Compressor oper-
ates at low speed
or stops.
Outdoor unit ther-
mistor short-circuit
error indication.
Normal operation. Outdoor unit ther-
mistor open-circuit
error indicatio
n.
Heating Expansion valve
control
Defrosting
Defrosting opera-
tion is not activated
as needed, and
frost accumulates
on outdoor unit
(expansion valve is
closed).
Outdoor unit ther-
mistor short-circuit
error indication.
Defrosting opera-
tion is activated
unnecessarily, and
room does not
become warm
(expansion valve is
open).
Outdoor unit ther-
mistor open-circuit
error indication.
Outside air temper-
ature thermistor
(TH3)
Aut
oO
peration mode
judgment
Cooling mode is
activated even if
room temperature
is low.
Outdoor unit ther-
mistor short-circuit
error indication.
Heating mode is
activated even if
room temperature
is high.
Outdoor unit ther-
mistor open-circuit
error indication.
Cooling
Dehumidifying
Operation not
affected
Normal operation. Outdoor unit ther-
mistor short-circuit
error indication.
Normal operation. Outdoor unit
ther-
mistor open-circu
it
error indication.
Heating Rating control
Defrosting
Defrosting opera-
tion is activated
unnecessarily.
Outdoor unit ther-
mistor short-circuit
error indication.
Defrosting opera-
tion is not activated,
and frost accumu-
lates on outdoor
unit.
Outdoor unit ther-
mistor open-circuit
error indication.
Suction pipe ther-
mistor (TH4)
Cooling
Dehumidifying
Expansion valve
control
Compressor oper-
ates, but room do
es
not become cool
(e
xpansion valve is
open).
Outdoor unit ther-
mistor short-circuit
error indication.
Frost accumulates
on evaporator inlet
section, and room
does not become
cool (expansion
valve is closed).
Outdoor unit ther-
mistor open-circuit
error indication.
Heating Expansion valve
control
Compressor oper-
ates, but room does
not become warm
(expansion valve is
open).
Outdoor unit ther-
mistor short-c
ircuit
error indication.
Frost accumulates
on expansion valve
outlet section, and
room does not
become warm
(expansion valve is
closed).
Outdoor unit ther-
mistor open-circuit
error indication.
2-way valve ther-
mistor (TH5)
Cooling
Dehumidifying
Expansion valve
control
Frost accumulates
on indoor unit evap-
orator and room
does not become
cool (expansion
valve is closed).
Outdoor unit ther-
mistor short-circuit
error ind
ication.
Compressor oper-
ates, but room does
not become cool
(expansion valve is
open).
Outdoor unit ther-
mistor open-circuit
error indication.
Heating Operation not
affected
Normal operation. Outdoor unit ther-
mistor short-circuit
error indication.
Normal operation. Outdoor unit ther-
mistor open-circuit
error indication.