Carrier 25VNA - TEMPERATURE SENSOR TROUBLESHOOTING; SCROLL TEMPERATURE DIAGNOSTICS

21
Start
Verify scroll temp
fault condition at
the system
controller
Disconnect 4-pin
plug from drive
(See Fig. 18)
Measure
resistance
between black &
white wires in the
4-pin plug
Is resistance
265Ω to 337KΩ?
Yes
No
Is resistance
265 Ω- 337KΩ ?
Allow time for
compressor to
cool & resistance
to change (60
minut es )
Is Ω moving towards
Ω corresponding to
ambient temp ?
Resistance
is in the
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 black &
white wires in the
4-pin plug
Is resistance
0Ω?
A good
reading is
equal to
infinite Ω
Refer to
thermistor
resistance -
Figure
temperature data
(See Fig. 14)
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
(Figure 14)
Yes
Power down the
entire system for
2 minutes to
reboot the drive
Allow time for
resistance to
change (60
minut es )
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
scroll thermistor
circuit pins
Is resistance
0Ω?
Yes
No
Scroll thermistor
circuit is shorted
internally
-
replace
compressor
Inspect molded
plug assembly
for lead to lead
shorting
Install new
molded p lug
assembly and
carefully route
wires
A
(See Fig. 20)
A12036
Fig. 12 – Scroll Temp Troubleshooting -- Part 1