Carrier 40MPHA Service Manual page 18

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