Carrier 40MPHA - Page 18

18
ERROR DIAGNOSIS AND TROUBLESHOOTING WITHOUT ERROR CODE (CONT)
Table 12—Field Maintenance
Field Maintenance Electrical Circuit
Possible causes
of trouble
Power
failure
Blown
fuse or
varistor
Loose
connections
Shorted
or
broken
wires
Safety
device
opens
Faulty
thermostat/
room temp
sensor
Wrong setting
place of
temp
sensor
Faulty
transformer
Shorted
or open
capacitor
Faulty
magnetic
contact for
compressor
Faulty
magnetic
contact
for fan
Low
voltage
Faulty
stepping
motor
Shorted or
grounded
compressor
Shorted or
grounded
fan motor
Unit will not start ☆ ☆ ☆ ☆ ☆ ☆
Compressor will not
start however the
fan runs
☆ ☆ ☆ ☆ ☆
Compressor and
condenser
(outdoor) fan will
not start
☆ ☆ ☆
Evaporator (indoor)
fan will not start
☆ ☆ ☆ ☆
Condenser (out
door) fan will not
start
☆ ☆ ☆ ☆ ☆
Unit runs but
shortly stops
☆ ☆
Compress or short
cycles due to
overload
☆ ☆
High discharge
pressure
Low discharge
pressure
High suction
pressure
Low suction
pressure
Unit runs
continuously but
insufficient cooling
Too cool ☆ ☆
Compressor is
noisy
Horizontal louver
can not revolve
☆ ☆ ☆
Test method /
remedy
Test
voltage
Inspect
fuse type
& size
Inspect
connections -
tighten
Test circuits
with tester
Test
continuity of
safety device
Test
continuity
of thermostat /
sensor & wiring
Place the temp.
sensor at the
central of air in
let grille
Check
control
circuit with
tester
Check
capacitor
with tester
Test
continuity
of coil &
contacts
Test
continuity
of coil &
contacts
Test
voltage
Replace
the
stepping
motor
Check
resistance
with Megger
tester
Check
resistance
with Megger
tester