Carrier 25VNA - MOTOR TEMPERATURE DIAGNOSTICS

23
Start
Verify motor
temp fault
condition at the
system controller
Disconnect 4-pin
plug from drive
(See Fig. 18)
Measure
resistance
between red &
white wires in t he
4-pin plug
Is resistance
459Ω to 168KΩ ?
Yes
No
Is resistance
459Ω -168KΩ?
Allow time for
compressor to
cool & resistance
to change (60
minut es )
Is Ω moving towards
Ω corresponding to
ambient temp ?
Resistance
is in range
that will
allow
operation
Yes
No
Measure
resistance
between unit
ground and
black, white, &
red wires in the
plug
Is there continuity
to ground?
Yes
No
Is the system
operable ?
A
Yes
No
B
Is compressor
hot ?
A
Yes
No
Measure
resistance
between red &
white wires in the
4-pin plug
Is resistance
0Ω?
Refer to
thermistor
resistance -
temperature data
(See Fig. 15)
WARNING !
Disconnect &
lock- out power,
allow 2 minutes
for drive to
discharge
A
No
Yes
No
If problem still
exists, change
the compressor
Refer to
thermistor
resistance -
temperature data
Yes
Power down the
entire system for
2 minutes to
reboot the drive
Allow time for
resistance to
change (60
minutes )
WARNING !
Recover system
refrigerant
charge
Thermistor
circuit is
shorted
Remove the
molded plug from
the thermistor
fusite on the
compressor
(See Fig. 19)
Measure
resistance in
motor thermistor
circuit pins
(See Fig. 20 & 21)
Is resistance
0Ω?
Yes
No
Motor thermistor
circuit is shorted
internally - replace
compressor
Inspect molded
plug assembly
for lead to lead
shorting
Install new
molded p lu g
assembly and
carefully route
wires
A
C
Disconnect
yellow, black,
and red wires
from output
connections on
drive (See Fig. 23)
Verify motor
winding
continuity from
the yellow, black,
and red lead
ends
Check each leg
(yellow, black,
and red wires) to
ground
If any of the
above Ω readings
show open or
short to ground,
replace the plug
A11554
Fig. 14 – Motor Temp Fault Troubleshooting -- Part 1