Carrier 38MPRAQ09AA3 - Field Maintenance - Electrical Circuit Issues

SG-38MPRA-02 Specifications subject to change without notice. 23
ERROR DIAGNOSIS AND TROUBLESHOOTING WITHOUT ERROR CODE (continued)
Table 19 — 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
(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 /
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 inlet 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