Carrier VECTOR 6500 Operation & Service Manual page 201

Alarm
Steps
NO.
124 CHECK DEFROST TERM 1 SENSOR
•
TRIGGER–ON: Defrost Termination Temperature Sensor (1DTT) is not within the range of -53° to
+158°F (-47° to +70° C.)
•
UNIT CONTROL: Engine and standby:
If Alarm 122 is not active: alarm and initiate defrost if 1RAT is below 45°F (7.2°C).
If Alarm 122 is also active: alarm and initiate defrost if 1SAT is below 45°F (7.2°C).
Under both of the above conditions, defrost will end after 10 minutes.
If Alarms 122 and 123 are also both active: alarm and defrost will not be allowed.
•
RESET CONDITION: Auto Reset when 1DTT is in range or, alarm may be manually reset via
keypad or by turning the unit off, then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (see reset condition above). Operate the unit through the appropriate modes to see if
any active alarm occurs. Continue with the steps below as necessary.
1 Check Sensor
a. Inspect sensor & connectors.
b. Check sensor resistance. (See
Note 3, page 7−2.)
2 Check Sensor Wiring
a. Inspect harness & control box
connector pins & terminals. (1MP
& DP16, see wiring schematic
Section 10.)
b. Power up the microprocessor (see
Note 2 page 7−2). Disconnect
sensor from harness. Check for
2.5 VDC at harness plug between
pins.
62-11389
Alarm/Cause
7−68
Corrective Action
No damage to sensor.
No damage, moisture, or corrosion in connectors.
10,000 Ohms @ 77°F (25°C.) See Table 8−5 for
complete table of temperatures and resistance val-
ues.
No physical damage to harness.
No damage, moisture, or corrosion in connectors.
Voltage should be 2.5 VDC volts at harness plug
between pins. This verifies microprocessor output
and wiring connections to the sensor.