Carrier 17/19EX - Manual (Page 256)

Resistance Check
Turn off the control power and disconnect the terminal plug of the sensor in question from the
module. Measure sensor resistance between receptacles designated by the wiring diagram with
a digital ohmmeter. The resistance and corresponding temperature is listed in Table 9A or
Table 9B . Check the resistance of both wires to ground. This resistance should be infinite.
Voltage Drop
Using a digital voltmeter, the voltage drop across any energized sensor can be measured
while the control is energized. Table 9A or Table 9B lists the relationship between temperature
and sensor voltage drop (volts dc measured across the energized sensor). Exercise care when
measuring voltage to prevent damage to the sensor leads, connector plugs, and modules.
Sensor wire should also be checked at the sensor plug connection. Check the sensor wire by
removing the condenser at the sensor and measure for 5 vdc back to the module if the control is
powered.
CAUTION CAUTION
!
Relieve all refrigerant pressure or drain the water prior to replacing the tempera-
ture sensors.