Carrier 40MPHA Service Manual page 21

ERROR DIAGNOSIS AND TROUBLESHOOTING WITHOUT ERROR CODE (continued)
Field
Maintenance
Possible
Blown fuse
causes Power failure
or varistor connections
of trouble
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
(outdoor) 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 / Inspect fuse
Test voltage connections -
remedy type & size
Table 12 — Field Maintenance
Faulty
Loose Shorted or Safety device thermostat/
broken wires opens room temp
sensor
☆ ☆ ☆
☆ ☆
☆ ☆
☆
☆ ☆
☆
☆ ☆
Test continuity
Inspect Test continuity
Test circuits of thermostat /
of safety
with tester sensor &
tighten device
wiring
Electrical Circuit
Faulty
Wrong setting
Faulty Shorted or magnetic
place of temp
transformer open capacitor contact for
sensor
compressor
☆
☆
☆
☆
☆
Place the
temp. sensor Check control Check Test continuity
at the central circuit with capacitor with of coil &
of air in- let tester tester contacts
grille
Faulty
Faulty
magnetic Low voltage
stepping motor
contact for fan
☆
☆
☆
☆
☆ ☆
☆ ☆
☆
Test continuity
Replace the
of coil & Test voltage
stepping motor
contacts
Shorted or Shorted or
grounded grounded fan
compressor motor
☆
☆
☆
Check Check
resistance with resistance with
Megger tester Megger tester