Carrier 69NT40-541-505, Operation And Service Manual, Page: 116 / 143

T-368 7–24
Due to the variations and inaccuracies in ohmmeters,
thermometers, or other test equipment, a reading
within 2% of the chart value would indicate a good sen-
sor. If a sensor is defective, the resistance reading will
usually be much higher or lower than the resistance
values given.
7.21.2 Sensor Replacement
a. Turn unit power OFF and disconnect power supply.
b. For two wire sensors, cut cable 5cm (2 inches)
from shoulder of defective sensor and discard
the defective sensor only. For 3-wire sensors,
cut at 23cm (9 inches). Slide the cap and grom-
met off well mounted sensor and save for possi-
ble reuse. Do not cut the grommet.
c. If required, prepare the replacement sensor by
cutting sensor wire(s) back 40mm (1-1/2 inch).
For 3-wire sensors, the black wire should be cut
at the middle length and the red/white wire cut to
the shorter length (See
Figure 7.26 ).
Figure 7.26 Sensor Types
d. Prepare the cables by cutting wires to the oppo-
site of the sensor (See Figure 7.27 ).
When installing a single wire color two wire sensor, cut
one wire of existing two wire cable 40mm (1-1/2 inch)
shorter than the other wire.
When replacing two single sensors with a combination
(3-wire) sensor, the black wires of the cables should be
cut to the same length and the red wire of one cable cut
to the shorter length.
When replacing a original 3-wire sensor, cut the black wire
to the middle length and the red wire to the shorter length.
e. Strip back insulation on all wiring 6.3mm (1/4
inch).
f. Slide a large piece of heat shrink tubing over the
cable, and place small pieces of heat shrink tub-
ing, one over each wire, before adding crimp fit-
tings as shown in
Figure 7.27 .
g. If required, slide the cap and grommet assembly
onto the replacement sensor. If the replacement
sensor is of a larger diameter than the original, a
different grommet may be required.
h. Slip crimp fittings over dressed wires (keeping
wire colors together). Make sure wires are
pushed into crimp fittings as far as possible and
crimp with crimping tool.
i. Solder spliced wires with a 60% tin and 40%
lead Rosincore solder.
j. Slide heat shrink tubing over splice so that ends
of tubing cover both ends of crimp as shown in
Figure 7.27 .
k. Heat tubing to shrink over splice. Make sure all
seams are sealed tightly against the wiring to
prevent moisture seepage.
l. Slide large heat shrink tubing over both splices
and shrink.
CAUTION
!
Do not allow moisture to enter wire splice
area as this may affect sensor resistance.
m.Reinstall sensor, refer to
Section
7.21.3 .
NOTE
The P5 Pre-Trip test must be run to inacti-
vate probe alarms (refer to
Section 5.7 ).
Figure 7.27 Sensor and Cable Splice
Sensor
40 mm (1 1/2 inch)
6.3 mm (1/4 inch)
Mounting Stud Type
Sensor
40 mm (1-1/2 inches)
6.3 mm (1/4 inch)
Bulb Type
Sensor
Cables
Heat Shrink Tubing
Large Heat Shrink Tubing
REPLACEMENT 2 WIRE TO 2 WIRE OR 3 WIRE TO 3 WIRE
REPLACEMENT FOR DUAL, SINGLE SENSOR CONFIGURATION
RED
BLACK
RED/WHITE
Cable
Sensor
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