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9. Allow pressures and temperatures to stabilize before
taking any measured reading (this may take up to 10
minutes).
10. Record all of the readings with the
Y1
and
Y2
demand.
11. If temperatures and pressures change in the direction
noted in chart, the compressor is properly modulating
from low to high capacity. (If no amperage, pressures
or temperature readings change when this test is
performed, the compressor is not switching between
low and high capacity and replacement is necessary).
12. After testing is complete, return unit to original set up.
DEFROST SYSTEM SENSORS
All three sensors are connected directly to the DCB via a
field-replaceable harness assembly that plugs directly to
the DCB.
The DCB monitors the attached sensors for the following
fault temperature conditions:
S
Coil
S
Discharge Line
S
Ambient Air
As the detected temperature changes, the resistance
across the sensor changes. Figure 25 shows how the
resistance varies as the temperature changes for both
type of sensors. Sensor resistance values can be checked
by ohming across pins shown in Table 10.
Table 10. Sensor Temperature / Resistance Range
Sensor
Temperature
Range °F (°C)
Resistance values
range (ohms)
Pins/Wire
Color
Outdoor
(Ambient)
−35 (−37) to 120
(48)
280,000 to 3750
3 and 4
(Black)
Coil
−35 (−37) to 120
(48)
280,000 to 3750
5 and 6
(Brown)
Discharge (if
applicable)
24 (−4) to 350
(176)
41,000 to 103
1 and 2
(Yellow)
NOTE
Sensor resistance decreases as sensed temperature in-
creases (see Figure25).
NOTE When checking the ohms across a sensor, be
aware that a sensor showing a resistance value that is not
within the range shown in Table 10, still perform as
designed. However, if a shorted or open circuit is detected,
then the sensor may be faulty and the sensor harness will
need to be replaced.
