Carrier VECTOR 6500 Operation & Service Manual page 199

Alarm
Steps
NO.
122 CHECK RETURN AIR SENSOR
•
TRIGGER–ON: Return Air Temperature Sensor (1RAT) is not within the range of -53 to +158°F (-47
to +70° C.)
•
UNIT CONTROL:Engine and Standby Operation:
If Alarm 123 - Check Supply Air Sensor - is not active: alarm only and switch to supply air control.
If Alarm 123 is also active (Cargo Protect Mode, refer to section 4.8.1) and the functional parameter
Temperature Control is set for Return Air and the set point is in the perishable range: alarm and
shutdown.
If Alarm 123 is also active (Cargo Protect Mode, refer to section 4.8.1) and set point is frozen:
alarm and unit will operate in reduced capacity COOL mode. (Refer to Section 4.8.1.)
•
RESET CONDITION: Auto Reset when Return Air Sensor 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
7−66
Corrective Action
No damage to sensor
No damage, moisture, or corrosion in connectors.
10,000 Ohms @ 77°F (25°C.) Refer to Table 8−5 for
complete table of temperatures and resistance
values.
No physical damage to harness.
No damage, moisture, or corrosion in connectors.
Voltage should be 2.5 VDC volts at harness plug be-
tween pins. This verifies microprocessor output and
wiring connections to the sensor.